V2X transmission resource selecting method implemented by terminal in wireless communication system and terminal using same

ABSTRACT

The present invention provides a V2X operation method implemented by a V2X (vehicle-to-X) terminal in a wireless communication system, the method characterized by: receiving information which indicates that another communication is implemented on V2X resources; and transmitting a V2X message on the basis of the information, wherein a V2X terminal is a terminal having limited capability to detect the implementation of the other communication on the V2X resources.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. § 371 ofInternational Application No. PCT/KR2017/002412, filed on Mar. 6, 2017,which claims the benefit of U.S. Provisional Applications No. 62/303,389filed on Mar. 4, 2016, No. 62/316,574 filed on Apr. 1, 2016, No.62/321,748 filed on Apr. 13, 2016, No. 62/333,862 filed on May 10, 2016,No. 62/350,727 filed on Jun. 16, 2016, No. 62/379,221 filed on Aug. 24,2016, No. 62/401,743 filed on Sep. 29, 2016, No. 62/403,028 filed onSep. 30, 2016, No. 62/416,669 filed on Nov. 2, 2016, and No. 62/423,738filed on Nov. 17, 2016, the contents of which are all herebyincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to wireless communications and, morespecifically, to a method of selecting a Vehicle-to-Everything (V2X)transmission resource by a user equipment (UE) in a wirelesscommunication system and a UE using the same.

Related Art

In the International Telecommunication Union Radio Communication Sector(ITU-R), standardization of International Mobile Telecommunication(IMT)-Advanced, a next generation mobile communication system after 3rdgeneration, is underway. IMT-Advanced aims to support IP (InternetProtocol) based multimedia service at data rates of 1 Gbps in astationary and low-speed moving state and 100 Mbps in a high-speedmoving state.

The 3rd Generation Partnership Project (3GPP) is a system standard thatmeets the requirements of IMT-Advanced, and LTE-Advanced (LTE-A), whichhas improved Long Term Evolution (LTE) based on Orthogonal FrequencyDivision Multiple Access (OFDMA)/Single Carrier-LTE-Advanced (LTE-A), isbeing prepared. LTE-A is one of the strong candidates for IMT-Advanced.

Recently, there has been a growing interest in D2D (Device-to-Device)technology for direct communication between devices. In particular, D2Dis attracting attention as a communication technology for the publicsafety network. Commercial communication networks are rapidly changingto LTE, but current public safety networks are mainly based on 2Gtechnology in terms of conflicts with existing communication standardsand cost. These technological gaps and demands for improved serviceshave led to efforts to improve public safety networks.

Public safety networks have higher service requirements (reliability andsecurity) than commercial communication networks and require directsignal transmission and reception, or D2D operation, between devices,especially when the coverage of cellular communications is insufficientor unavailable.

For example, D2D operation in general can have a variety of advantagesin that it transmits and receives signals between nearby devices. Forexample, the D2D UE has high data rate and low delay and is capable ofdata communication. Also, the D2D operation can disperse the traffic tothe base station, and can also expand the coverage of the base stationif the UE performing the D2D operation acts as a repeater.

The D2D communication may expand and be applicable for signaltransmission and reception between vehicles, and vehicle-relatedcommunication is referred to as Vehicle-To-Everything (V2X)communication.

The term “x” in V2X means pedestrian (communication between a vehicleand a device carried by an individual (e.g.,) handheld terminal carriedby a pedestrian, cyclist, driver or passenger)) (V2P), vehicle(communication between vehicles) (V2V), infrastructure/network(communication between a vehicle and a roadside unit (RSU)/network(e.g.,) RSU is a transportation infrastructure entity (e.g.,) an entitytransmitting speed notifications) implemented in an eNB or a stationaryUE)) (V2I/N

A (V2P communication-related) device carried by a pedestrian (or human)will be referred to as “P-UE”, and a (V2X-communication-related) deviceinstalled at a vehicle will be referred to as “V-UE”. In addition, forexample, the term “entity” in the present invention may be understood asa P-UE and/or a V-UE and/or RSU (network/infrastructure).

Meanwhile, in V2X communication, the question may be which resource tobe selected when a P-UE transmits a V2X signal. The P-UE is sensitive tobattery consumption, compared with a UE installed at a vehicle. Inaddition, in 2X communication, it may be important to periodicallytransmit a signal without interfering other UEs. A method for selectinga transmission resource by a P-UE needs to be determined inconsideration of the above.

SUMMARY OF THE INVENTION

The present invention provides a method of selecting aVehicle-to-Everything (V2X) transmission resource by a User Equipment(UE) in a wireless communication system, and a UE using the same.

In an aspect, a method for Vehicle-to-X (V2X) operation in a wirelesscommunication system is provided. The method may be performed by a V2XUser Equipment (UE) and comprise receiving information indicating thatanother communication is implemented on a V2X resource and transmittinga V2X message on the basis of the information. The V2X UE may be a UEhaving a limited capability of detecting the implementation of theanother communication on the V2X resource.

The UE having the capability of detecting the implementation of theanother communication may be a UE having a limited sensing capability, aUE having no sensing capability, or a UE having no reception chaindedicated to the V2X resource.

The UE having the limited capability of detecting the implementation ofthe another communication may be a Pedestrian User Equipment (P-UE).

The V2X UE may receive, from a different V2X UE or from a base station,the information that another communication is implemented on the V2Xresource.

The information indicating that another communication may be implementedon the V2X resource is information indicating a type of a sidelinkservice which is performed on the V2X resource.

The information indicating that another communication may be implementedon the V2X resource is information indicating whether or not a servicebeing performed on the V2X resource is a public safety (PS) service.

The information indicating that another communication may be implementedon the V2X resource is information indicating whether or notcommunication based on a radio access technology (RAT) different from aRAT of V2X communication is implemented on the V2X resource.

When another communication is implemented on the V2X resource, the V2XUE may switch a resource for transmission of the V2X message to adifferent V2X resource, and the V2X UE may transmit the V2X message onthe switched different V2X resource.

The V2X UE may transmit the V2X message on the switched different V2Xresource for a preset period of time.

The switched different V2X resource may be a subframe other than asubframe used by the V2X UE in a previously transmitted Transport Block(TB).

The V2X resource may be a V2X resource pool, a V2X carrier, a V2Xchannel, or a V2X band.

In another aspect, a User Equipment (UE) is provide. The UE may comprisea Radio Frequency (RF) unit configured to transmit and receive a radiosignal and a processor configured to operate in conjunction with the RFunit, the processor may receive information indicating that anothercommunication is implemented on a Vehicle-to-X (V2X) resource, andtransmit a V2X message on the basis of the information. The UE may be aUE having a limited capability of detecting the implementation of theanother communication on the V2X resource.

According to the present invention, a P-UE which is sensitive to batteryconsumption performs partial sensing to select a V2X transmissionresource, thereby enabled to reduce battery consumption. In addition, IfV2X transmission resources are selected multiple times, the sameresource as previously selected resources are excluded from theselection, and therefore, it is possible to alleviate a half-duplexproblem.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system to which the presentinvention is applied.

FIG. 2 is a diagram showing a wireless protocol architecture for a userplane.

FIG. 3 is a diagram showing a wireless protocol architecture for acontrol plane.

FIG. 4 illustrates a reference structure for a ProSe.

FIG. 5 illustrates arrangement examples of terminals performing ProSedirect communication and cell coverage.

FIG. 6 illustrates a user plane protocol stack for the ProSe directcommunication.

FIG. 7 illustrates a PC 5 interface for D2D discovery.

FIG. 8 illustrates an example of a LTE SL V2V detection signal usingtime repetition of a short sequence.

FIG. 9 illustrates an example of an LTE SL V2V detection signal usingsequence matching in a frequency domain.

FIG. 10 shows an example of a V2X transmission resource (re)selection(or reservation) in a partial sensing operation according to <ProposedMethod #2>.

FIG. 11 shows an example of (re)determining (or selecting/reserving) aV2X transmission subframe (or resource) according to <Proposed Method#2>.

FIG. 12 illustrates a method of communication among a P-UE, a V-UE, anda network according to <Proposed Method #2>.

FIG. 13 illustrates an example of a method of (re)selecting (orreserving) a V2X transmission resource according to Example #4-1.

FIG. 14 illustrates a method of (re)selecting (or reserving) V2Xtransmission resource according to Example #4-1.

FIG. 15 illustrates an example of a type of a V2X transmission resourcepool.

FIG. 16 illustrates an example of a method of selecting a V2X pool whenresource pools of multiple types exist.

FIG. 17 illustrates an example of an operation that randomly selects aresource in a (partial) sensing-allowed resource pool.

FIG. 18 is a flowchart of a method by which a UE having a limited RXcapability transmits a V2X message according to an embodiment of thepresent invention.

FIG. 19 is a flowchart of a method for transmitting a V2X message by aUE having a limited RX capability, according to another embodiment ofthe present invention.

FIG. 20 is a flowchart of a method of transmitting a V2X message by a UEhaving a limited RX capability, according to another embodiment of thepresent invention.

FIG. 21 is a flowchart of a V2X transmission method according to anembodiment of the present invention when WAN transmission and V2Xtransmission overlap in a time domain.

FIG. 22 schematically illustrates an example in which V2X transmissionand WAN (UL) transmission (partially or entirely) overlap in a timedomain on different carriers.

FIG. 23 is a flowchart of a V2X transmission method according to anotherembodiment of the present invention in the case where WAN transmissionand V2X transmission overlap in a time domain.

FIG. 24 illustrates an example of a method for prioritizing V2Xtransmission (which overlaps with WAN (UL) transmission on a time domainon the same (and/or different) carrier) over a WAN (UL) transmission.

FIG. 25 is a flowchart of a V2X transmission method according to anotherembodiment of the present invention in the case where a WAN transmissionoperation and a V2X transmission operation overlap in a time domain.

FIG. 26 is a block diagram of a UE that implements an embodiment of thepresent invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows a wireless communication system to which the presentinvention is applied. The wireless communication system may also bereferred to as an evolved-UMTS terrestrial radio access network(E-UTRAN) or a long term evolution (LTE)/LTE-A system.

The E-UTRAN includes at least one base station (BS) 20 which provides acontrol plane and a user plane to a user equipment (UE) 10. The UE 10may be fixed or mobile, and may be referred to as another terminology,such as a mobile station (MS), a user terminal (UT), a subscriberstation (SS), a mobile terminal (MT), a wireless device, etc. The BS 20is generally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as an evolved node-B (eNB), abase transceiver system (BTS), an access point, etc.

The BSs 20 are interconnected by means of an X2 interface. The BSs 20are also connected by means of an S1 interface to an evolved packet core(EPC) 30, more specifically, to a mobility management entity (MME)through S1-MME and to a serving gateway (S-GW) through S1-U.

The EPC 30 includes an MME, an S-GW, and a packet data network-gateway(P-GW). The MME has access information of the UE or capabilityinformation of the UE, and such information is generally used formobility management of the UE. The S-GW is a gateway having an E-UTRANas an end point. The P-GW is a gateway having a PDN as an end point.

Layers of a radio interface protocol between the UE and the network canbe classified into a first layer (L1), a second layer (L2), and a thirdlayer (L3) based on the lower three layers of the open systeminterconnection (OSI) model that is well-known in the communicationsystem. Among them, a physical (PHY) layer belonging to the first layerprovides an information transfer service by using a physical channel,and a radio resource control (RRC) layer belonging to the third layerserves to control a radio resource between the UE and the network. Forthis, the RRC layer exchanges an RRC message between the UE and the BS.

FIG. 2 is a diagram showing a wireless protocol architecture for a userplane. FIG. 3 is a diagram showing a wireless protocol architecture fora control plane. The user plane is a protocol stack for user datatransmission. The control plane is a protocol stack for control signaltransmission.

Referring to FIGS. 2 and 3, a PHY layer provides an upper layer with aninformation transfer service through a physical channel. The PHY layeris connected to a medium access control (MAC) layer which is an upperlayer of the PHY layer through a transport channel. Data is transferredbetween the MAC layer and the PHY layer through the transport channel.The transport channel is classified according to how and with whatcharacteristics data is transferred through a radio interface.

Data is moved between different PHY layers, that is, the PHY layers of atransmitter and a receiver, through a physical channel. The physicalchannel may be modulated according to an Orthogonal Frequency DivisionMultiplexing (OFDM) scheme, and use the time and frequency as radioresources.

The functions of the MAC layer include mapping between a logical channeland a transport channel and multiplexing and demultiplexing to atransport block that is provided through a physical channel on thetransport channel of a MAC Service Data Unit (SDU) that belongs to alogical channel. The MAC layer provides service to a Radio Link Control(RLC) layer through the logical channel.

The functions of the RLC layer include the concatenation, segmentation,and reassembly of an RLC SDU. In order to guarantee various types ofQuality of Service (QoS) required by a Radio Bearer (RB), the RLC layerprovides three types of operation mode: Transparent Mode (TM),Unacknowledged Mode (UM), and Acknowledged Mode (AM). AM RLC provideserror correction through an Automatic Repeat Request (ARQ).

The RRC layer is defined only on the control plane. The RRC layer isrelated to the configuration, reconfiguration, and release of radiobearers, and is responsible for control of logical channels, transportchannels, and PHY channels. An RB means a logical route that is providedby the first layer (PHY layer) and the second layers (MAC layer, the RLClayer, and the PDCP layer) in order to transfer data between UE and anetwork.

The function of a Packet Data Convergence Protocol (PDCP) layer on theuser plane includes the transfer of user data and header compression andciphering. The function of the PDCP layer on the user plane furtherincludes the transfer and encryption/integrity protection of controlplane data.

What an RB is configured means a procedure of defining thecharacteristics of a wireless protocol layer and channels in order toprovide specific service and configuring each detailed parameter andoperating method. An RB can be divided into two types of a Signaling RB(SRB) and a Data RB (DRB). The SRB is used as a passage through which anRRC message is transmitted on the control plane, and the DRB is used asa passage through which user data is transmitted on the user plane.

If RRC connection is established between the RRC layer of UE and the RRClayer of an E-UTRAN, the UE is in the RRC connected state. If not, theUE is in the RRC idle state.

A downlink transport channel through which data is transmitted from anetwork to UE includes a broadcast channel (BCH) through which systeminformation is transmitted and a downlink shared channel (SCH) throughwhich user traffic or control messages are transmitted. Traffic or acontrol message for downlink multicast or broadcast service may betransmitted through the downlink SCH, or may be transmitted through anadditional downlink multicast channel (MCH). Meanwhile, an uplinktransport channel through which data is transmitted from UE to a networkincludes a random access channel (RACH) through which an initial controlmessage is transmitted and an uplink shared channel (SCH) through whichuser traffic or control messages are transmitted.

Logical channels that are placed over the transport channel and that aremapped to the transport channel include a broadcast control channel(BCCH), a paging control channel (PCCH), a common control channel(CCCH), a multicast control channel (MCCH), and a multicast trafficchannel (MTCH).

The physical channel includes several OFDM symbols in the time domainand several subcarriers in the frequency domain. One subframe includes aplurality of OFDM symbols in the time domain. An RB is a resourcesallocation unit, and includes a plurality of OFDM symbols and aplurality of subcarriers. Furthermore, each subframe may use specificsubcarriers of specific OFDM symbols (e.g., the first OFDM symbol) ofthe corresponding subframe for a physical downlink control channel(PDCCH), that is, an L1/L2 control channel. A Transmission Time Interval(TTI) is a unit time for subframe transmission.

Hereinafter, a D2D operation will be described. In the 3GPP LTE-A, aservice related to the D2D operation refers to Proximity based Services(ProSe). Hereinafter, the ProSe is an equivalent concept with the D2Doperation and the ProSe may be compatibly used with the D2D operation.The ProSe is now described.

The ProSe includes ProSe direct communication and ProSe directdiscovery. The ProSe direct communication presents communicationperformed by two or more adjacent terminals. The terminals may performcommunication using a protocol of a user plane. A ProSe-enabled UE meansa UE for supporting a process related to requirements of the ProSe.Unless otherwise defined, the ProSe-enabled UE includes both of a publicsafety UE and a non-public safety UE. The public safety UE represents aUE for supporting both of a public safety specified function and theProSe process. The non-public safety UE is a terminal which supports theProSe process but does not support the public safety specified function.

The ProSe direct discovery is a process where the ProSe-enabled UEdiscovers another ProSe-enabled UE. In this case, only ability of thetwo ProSe-enabled UEs is used. An EPC-level ProSe discovery signifies aprocess where an EPC determines whether 2 ProSe enable terminals areclosed to each other, and reports the close state thereof the two ProSeenabled terminals.

Hereinafter, the ProSe direct communication may refer to D2Dcommunication, and the ProSe direct discovery may refer to D2Ddiscovery.

FIG. 4 illustrates a reference structure for a ProSe.

Referring to FIG. 4, the reference structure for a ProSe includes aplurality of terminals having E-UTRAN, EPC, and ProSe applicationprogram, a ProSe application (APP) server, and a ProSe function.

An EPC is a representative example of the E-UTRAN. The EPC may includean MME, an S-GW, a P-GW, a policy and charging rules function (PCRF),and a home subscriber server (HSS).

The ProSe application server is a user of ProSe in order to make anapplication function. The ProSe application server may communicate withan application program in the terminal. The application program in theterminal may use a ProSe ability to make an application function.

The ProSe function may include at least one of following functions butis not limited thereto.

Interworking via a reference point towards the 3rd party applications

Authorization and configuration of the UE for discovery and directcommunication)

Enable the function of the EPC level ProSe discovery

ProSe related new subscriber data and handling of data storage, and alsohandling of ProSe identities

Security related function

Provide control towards the EPC for policy related function

Provide function for charging (via or outside of EPC, e.g., offlinecharging))

Hereinafter, a reference point and a reference interface will bedescribed in a reference structure for the ProSe.

PC1: a reference point between a ProSe application program in theterminal and a ProSe application program in a ProSe application server.The PC1 is used to define signaling requirements in an applicationlevel.

PC2: is a reference point between the ProSe application server and aProSe function. The PC2 is used to define an interaction between theProSe application server and a ProSe function. An application dataupdate of a ProSe database of the ProSe function may be an example ofthe interaction.

PC3: is a reference point between the terminal and the ProSe function.The PC3 is used to define an interaction between the terminal and theProSe function. Configuration for ProSe discovery and communication maybe an example of the interaction.

PC4: is a reference point between an EPC and the ProSe function. The PC4is used to define an interaction between the EPC and the ProSe function.The interaction lay illustrate when a path for 1:1 communication or aProSe service for real time session management or mobility managementare authorized.

PC5: is a reference point to use control/user plane for discovery,communication, and relay between terminals, and 1:1 communication.

PC6: is a reference point to use a function such as ProSe discoverybetween users included in different PLMNs.

SGi: may be used for application data and application level controlinformation exchange.

<ProSe Direct Communication (D2D Communication)>.

The ProSe direct communication is a communication mode where two publicsafety terminals may perform direct communication through a PC 5interface. The communication mode may be supported in both of a case ofreceiving a service in coverage of E-UTRAN or a case of separating thecoverage of E-UTRAN.

FIG. 5 illustrates arrangement examples of terminals performing ProSedirect communication and cell coverage.

Referring to FIG. 5(a), UEs A and B may be located outside of the cellcoverage. Referring to FIG. 5(b), the UE A may be located in the cellcoverage and the UE B may be located outside of the cell coverage.Referring to FIG. 5(c), both of UEs A and B may be located in the cellcoverage. Referring to FIG. 5(d), the UE A may be located in coverage ofa first cell and the UE B may be in coverage of a second cell.

As described above, the ProSe direct communication may be performedbetween terminals which are provided at various positions.

Meanwhile, following IDs may be used in the ProSe direct communication.

Source layer-2 ID: The source layer-2 ID identifies a sender of a packetin a PC 5 interface.

Purpose layer-2 ID: The purpose layer-2 ID identifies a target of apacket in a PC 5 interface.

SA L1 ID: The SA L1 ID represents an in an ID in a scheduling assignment(SA) in the PC 5 interface.

FIG. 6 illustrates a user plane protocol stack for the ProSe directcommunication.

Referring to FIG. 6, the PC 5 interface includes a PDCH layer, a RLClayer, a MAC layer, and a PHY layer.

There may not be HARQ feedback in the ProSe direct communication. An MACheader may include the source layer-2 ID and the purpose layer-2 ID.

<Radio Resource Assignment for ProSe Direct Communication>.

A ProSe enable terminal may use following two modes with respect toresource assignments for the ProSe direct communication.

1. Mode 1

The mode 2 is a mode for receiving scheduling a resource for the ProSedirect communication from a base station. The terminal should be in aRRC_CONNECTED state according to the mode 1 in order to transmit data.The terminal requests a transmission resource to the base station, andthe base station schedules a resource for scheduling assignment and datatransmission. The terminal may transmit a scheduling request to the basestation and may transmit a Buffer Status Report (ProSe BSR). The basestation has data which the terminal will perform the ProSe directcommunication and determines whether a resource for transmitting thedata is required.

2. Mode 2

The mode 2 is a mode for selecting a direct resource. The terminaldirectly selects a resource for the ProSe direct communication from aresource pool. The resource pool may be configured by a network or maybe previously determined.

Meanwhile, when the terminal includes a serving cell, that is, when theterminal is in an RRC_CONNECTED state with the base station or islocated in a specific cell in an RRC_IDLE state, the terminal isregarded to be in coverage of the base station.

If the terminal is located outside of the coverage, only the mode 2 isapplicable. If the terminal is located in the coverage, the mode 1 orthe mode 2 may be used according to setting of the base station.

If there are no exceptional conditions, only when the base station isconfigured, the terminal may change a mode from the mode 1 to the mode 2or from the mode 2 to the mode 1.

<ProSe Direct Discovery (D2D Discovery)>

The ProSe direct discovery represents a process used to discover whenthe ProSe enabled terminal discovers other neighboring ProSe enabledterminal and refers to D2D direction discovery or D2D discovery. In thiscase, an E-UTRA wireless signal through the PC 4 interface may be used.Hereinafter, information used for the ProSe direct discovery refers todiscovery information.

FIG. 7 illustrates a PC 5 interface for D2D discovery.

Referring to FIG. 7, the PC 5 interface includes an MAC layer, a PHYlayer, and a ProSe Protocol layer being an upper layer. Permission forannouncement and monitoring of discovery information is handled in theupper layer ProSe Protocol. Contents of discovery information aretransparent to an access stratum (AS). The ProSe Protocol allows onlyvalid discovery information to be transferred to the AS forannouncement.

An MAC layer receives discovery information from the upper layer ProSeProtocol. An IP layer is not used for transmitting the discoveryinformation. The MAC layer determines a resource used in order toannounce the discovery information received from the upper layer. TheMAC layer makes and sends a protocol data unit (MAC PDU) to a physicallayer. An MAC header is not added.

There are two types of resource assignments for announcing the discoveryinformation.

1. Type 1

The type 1 is a method assigned so that resources for announcing thediscovery information are not terminal-specific and the base stationprovides resource pool configuration for announcing the discoveryinformation to the terminals. The configuration may be included in asystem information block (SIB) to be signaled in a broadcast scheme.Alternatively, the configuration may be included in a terminal specificRRC message to be provided. Alternatively, the configuration may bebroadcast-signaled or terminal-specific signaled of a different layerfrom the RRC message.

The terminal selects a resource from an indicated resource pool toannounce discovery information using the selected resource. The terminalmay announce discovery information through a resource optionallyselected during each discovery period.

2. Type 2

The type 2 is a method where resources for announcing the discoveryinformation are terminal-specifically assigned. A terminal in aRRC_CONNECTED state may request a resource for announcing a discoverysignal to the base station through a RRC signal. The base station mayassign a resource for announcing a discovery signal as an RRC signal. Aresource for monitoring the discovery signal in a configured resourcepool may be assigned in terminals.

With respect to a terminal in an RRC_IDLE state, a base station mayreport a type 1 resource pool for announcing the discovery signal as anSIB. Terminals where ProSe direct discovery is allowed use a type 1resource pool for announcing the discovery information in the RRC IDLEstate. Alternatively, the base station 2) reports that the base stationsupports the ProSe direct discovery through the SIB but may not providethe resource for announcing the discovery information. In this case, theterminal should enter the RRC_CONNECTED state for announcing thediscovery information.

With respect to a terminal in an RRC_CONNECTED state, the base stationmay configure whether to use a type 1 resource pool or a type 2 resourcepool for announcing the discovery information through a RRC signal.

As described above, a D2D operation generally has various advantages inthat the D2D operation is signal transmission/reception betweenneighboring devices. For example, a D2D terminal has a high data rateand a low latency and is capable of data communication. In addition, theD2D operation can enable distribution of traffic concentrated on a basestation, and thus, if the D2D terminal serves as a relay, the D2Doperation can expand the coverage of the base station. An expandedversion of the above-described D2D communication includes includingsignal transmission/reception between vehicles, and a communicationtechnology relating to vehicles is called Vehicle-To-X (V2X)communication.

Herein, for example, the term “X” in V2X means pedestrian (communicationbetween a vehicle and a device carried by an individual (for example)handheld terminal carried by a pedestrian, cyclist, driver orpassenger)) (V2P), vehicle (communication between vehicles) (V2V),infrastructure/network (communication between a vehicle and a roadsideunit (RSU)/network (for example) RSU is a transportation infrastructureentity (for example) an entity transmitting speed notifications)implemented in an eNB or a stationary UE)) (V2I/N). In addition, forexample, for convenience of explanation of a proposed method, a (V2Pcommunication-related) device carried by a pedestrian (or human) will bereferred to as “P-UE”, and a (V2X communication-related) deviceinstalled at a vehicle will be referred to as “V-UE”. In addition, forexample, the term “entity” in the present invention may be understood asa P-UE and/or a V-UE and/or RSU(network/infrastructure).

A UE providing (or supporting) the above-described D2D operation may bereferred to a D2D UE, and a UE providing (or supporting) theabove-described V2X operation may be referred to as a V2X UE.Hereinafter, for convenience of explanation, embodiments of the presentinvention will be described mainly from the perspective of the V2X UE,but description about the V2X UE may apply even to the D2D UE.

The V2X UE may transmit a message (or channel) on a predefined (orsignaled) resource pool. Herein, the resource pool may indicate aresource(s) which is pre-defined for a UE to perform a V2X operation (orto be capable of performing a V2X operation). The resource poll may be,for example, defined in terms of a time/frequency.

<Method for Allowing “V2X Communication” and “Another Communication” toCoexist>

The following methods for coexistence are proposed methods for allowing“V2X communication” and “another communication (e.g., DSRC/IEEE 802.11Pservice”, “(different numerology-based) NEW RAT (NR) eV2X service”) toefficiently coexist in the same channel (or band) which ispredefined(/signaled).

Herein, for example, when the following rules(methods) are applied, itis possible to effectively achieve “fairness” in “channel (or band)usage (or occupancy)” between different communications”

For example, the term “channel (band/resource)” used in the presentinvention may be understood as “carrier (frequency/pool)”.

[Coexistence method #1] A V2X UE(s) participating in “V2X communication”may omit an operation of transmitting a (V2X communication-related)channel/signal on a pre-defined (or signaled) specific (time/frequency)resource (herein, the omission can be understood as a kind of “silencingperiod”), and to perform an “(energy) measurement” operation.

Herein, for example, (corresponding) “silencing period” related (set)parameters (e.g., a period, a (time/frequency) resource location(length), and a hopping pattern) may be designated in the form of“carrier(pool) specific (pre)configuration”.

Herein, for example, using the corresponding “(energy) measurement”operation, it is possible to determine whether “another communication(e.g., “DSRC/IEEE 802.11P”, “(different numerology-based) NR eV2Xservice”)” is being implemented in a close distance (and/or the samechannel (band)).

Herein, for example, a rule may be defined such that, if an “(energy)measurement” value is higher than a predefined(signaled) thresholdvalue, it may be: (A) a V2X UE(s) stops “V2X communication” (for apre-defined(signaled) time); or (B) a V2X UE(s) performs “V2Xcommunication” (for a pre-defined(signaled) time) on a (correspondingchanged) different resource (or channel/band) which performs “V2X”communication according to the predefined(signaled) rule (priorityorder).

Herein, for example, if the “(energy) measurement” value is lower thanthe pre-defined(signaled) threshold value, the V2X UE(s) may keepperforming the “V2X communication” on the corresponding channel (band)without stopping.

Herein, for example, a (pre-defined (signaled)) (time/frequency)resource (e.g., “silencing period”) used to detect the “anothercommunication” (and/or “other RAT”) may not apply a V2X resource poolsetting-related (pre-set(signaled) length) bitmap.

Herein, for example, if the corresponding rule is applied, the(pre-defined (or signaled)) (time/frequency) resource used to detect“another communication” “(and/or “other RAT”) may be understood as beingexcluded from setting a V2X resource pool.

For example, a rule may be defined such that a V2X UE(s) informs itsneighboring “V2X UE(s)” (and/or a “(serving) base station (RSU)”) ofinformation on detection (or non-detection) of “another communication”.

Herein, for example, when a UE reports the corresponding information,the UE's location information (and/or information on a resource pool (orcarrier/channel/band) (index) in which “another communication” isdetected (when location based resource pool (TDM (or FDM)) separation isset (or signaled).

Herein, for example, when receiving the information, a (serving) basestation (or RSU) may inform a V2X UE(s) (on a (reported) neighboring (oridentical) location (or region)) of the corresponding information (e.g.,informing a “P-UE(s)” of the corresponding information (through apre-defined signal (e.g., (WAN) DL (or PDSCH)).

Herein, for example, after receiving the corresponding information (froma V-UE(s)), a (serving) base station (or RSU) may instruct to switch toa different carrier (or channel/band/pool) on a (neighboring oridentical) location (or region) at which “another communication” isdetected (and/or a V2X UE(s) on a pool (or carrier/channel/band) (e.g.,by controlling a P-UE(s)” to perform “activation/deactivation” of a(related) resource pool, and/or by stopping “V2X communication” (and/orV2X message TX operation”), and or according to a pre-set (or signaled)rule (or a priority)).

Herein, in another example, after receiving corresponding information(from a serving base station (or RSU)), a V2X UE(s) (e.g., “P-UE(s)”)may consider (compare) its (current) location (and/or a pool (orcarrier/channel/band) on which the “P-UE(s)” performs (current) V2Xmessage TX operation) so as to decide (or determine) whether to maintain(or stop) the V2X message TX operation and/or whether to implement “V2Xcommunication” (and/or “V2X message TX operation”) on (the changed)different resource (or channel/band) (for a pre-set (or signaled)predetermined period of time) according to a pre-defined (or signaled)rule (or a priority).

Herein, for example, a rule may be defined to perform reporting (orsignaling) corresponding information (by a “V2X UE(s)”) only when a“(energy) measurement” value is higher than a pre-defined (or signaled)threshold value.

Herein, for example, after receiving (or being reported of) informationon detection of “another communication” from a V2X UE(s), a “(serving)base station (or RSU)” may instruct (1) to change a “carrier (orchannel/band) on which “V2X communication” is being implemented(according to a pre-defined (or signaled) rule (or a priority)) and/orto (B) change to “UU based V2X communication”.

Herein, for example, when receiving information on detection of “anothercommunication” from a (neighboring) adjacent V2X UE(s), a V2X UE(s)(also) changes a “channel (or band/carrier), on which “V2Xcommunication” is being implemented, according to a pre-defined (orsignaled) rule (or priority), and/or stops “V2X communication” on thecorresponding channel (or band/carrier) (for a pre-defined (signaled)period of time) (and/or performs “V2X communication” “on a channel (orband/carrier/resource) changed according to a pre-defined (or signaled)rule (or priority) (for a pre-set (or signaled) period of time).

For example, to efficiently receive the information (on detection of“another communication”) (re)transmitted (or relayed) by a (serving)base station (or RSU) (and/or a (different) V2X UE(s)), a V2X UE(s)(e.g., a P-UE(s)) may be controlled to “wake up” according to apre-defined (or signaled) period (or pattern) (regardless of “RRC idlestate”) and/or make an “attempt to receive a channel (or signal) usedfor that purpose”).

Herein, for example, a V2X UE(s) (e.g., a P-UE(s)) may receive (after“wake-up” operation) only “the (most) recent information-reflected (orincluded) (corresponding) channel (or signal) used for that purpose”transmitted at a point in time (period) prior to a resource which isselected (or reserved) for the purpose of V2X message TX (or itstransmission operation (time)) (or prior to a (time (or timing)) offsetvalue which is pre-set (or signaled) by a resource selected (orreserved) by the V2X UE(s) for the purpose of V2X MESSAGE TX (or whichis pre-set (or signaled) at its transmission operation (time)), and thenthe V2X UE(s) may be controlled to decide (or determine) whether toperform (final) “V2X communication” (and/or “V2X MESSAGE TX operation”on the basis of the corresponding (recent) information.

For example, a rule may be defined such that, if (“V2Xcommunication”-related) (pre-set (or signaled)) “LTE signal (orchannel)” is not detected on a pre-defined (or signaled) specific(time/frequency) resource) and (at the same time) an “(energy)measurement” value is higher than a pre-defined (or signaled) thresholdvalue, a V2X UE(s) determines that “another communication (e.g.,‘DSRC/IEEE 802.11P service”, “(different numerology-based) NR eV2Xservice”) is being implemented in a close distance (and/or the samechannel (or band)).

For example, when receiving information on detection (or non-detection)of “another communication” from a specific V2X UE(s), a (serving) basestation (or RSU) (and/or a (different) V2X UE(s)) may inform neighboring(other) V2X UE(s) (which has established connection within coverage)(e.g., “P-UE(s)”) (and/or the base station (or RSU)) of thecorresponding information through a pre-defined channel (or signal).

Herein, for example, such information may be transmitted along withadditional information such as pre-defined (or reported) “information ona location (or identifier) of a “specific V2X UE(s)” (and/or (whenlocation-based resource pool (TDM (or FDM)) separation operation is set(or signaled)) information on (an index of) a resource pool (orcarrier/channel/band), on which “another communication” detected, and/or“(energy) measurement information”).

For example, according to the rule, in the case of a V2X UE(s) which hasstopped “V2X communication” on an existing channel (or band) (for apre-defined (or signaled) period of time) (and/or which has implemented“V2X communication” on a different resource (or channel/band)), the V2XUE(s) may perform “(energy) measurement” operation again on a specific(time/frequency) resource, and, if “another communication” is notdetected”, the V2X UE(s) may implement “V2X communication” again (on theexisting channel (or band)).

In an additional example, a rule may be defined such that “V2Xcommunication” is implemented on an existing channel (or band) again (A)only when “another communication” is not detected (after “(energy)measurement” operation) and/or (B) only when a pre-defined (or signaled)back-off (or counter) value (“X”) is equal to or smaller than “0” (or arandom (failure) value selected (chosen) within a range of “0≤X≤1” isequal to or smaller than a pre-defined (or signaled) probability value).

Herein, for example, whenever “another communication” is not detected(in response to “(energy) measurement” operation), the back-off valuemay be reduced by a pre-defined (or signaled) value (e.g., “1”).

For example, an “(energy) measurement” operation for detecting anothercommunication (e.g., “‘DSRC/IEEE 802.11P service, “(differentnumerology-based) NR eV2X service”) needs to be implemented at the sametime by V2X UE(s) (located at least in a pre-defined (or signaled)distance).

Otherwise, for example, “V2X communication” (being implemented in aclose distance (and/or on the same channel (or band)) may bemisunderstood as “another communication”, and thus, “V2X communication”may be stopped excessively.

Accordingly, for example, a rule may be defined such that informationrelating to a (time/frequency) resource, on which “(energy) measurement”operation is being implemented, (e.g., a period, a subframe offset, a(hopping) pattern, etc.) is set (or signaled) and applied with referenceto “(instead of “local time”) Global Positioning System (GPS) time (orCoordinated Universal Time (UTC))” (or time (synchronization) of a“(serving) base station (or RSU)”).

Herein, for example, the information relating to a (time/frequency)resource on which “(energy) measurement” operation is being implementedmay be set (differently or independently) in consideration of “V2Xmessage type (e.g., “periodic” or event-triggered” V2X message) and/or“V2X message priority” and/or “V2X UE density (or speed)” and/or “V2Xmessage priority” and/or “V2X UE type”.

For example, the “(energy) measurement” operation may be performed(directly) by a (serving) base station (or RSU), (not just by a V2XUE(s)).

Herein, for example, when detecting “another communication (e.g.,“DSRC/IEEE 802.11P service”, “(different numerology-based) NR eV2Xservice)” in a close distance (and/or the same channel (or band)), a(serving) base station (or RSU) may inform (or instruct) a neighboringV2X UE(s) (which exists within coverage or which has establishedconnection) of whether “V2X communication” (on the corresponding channel(or band)) is stopped (and/or whether “V2X communication” is beingimplemented on a different resource (or channel/band) according to apre-defined (or signaled) rule (or priority)) (through a pre-definedchannel (or signal)).

In another example, when “cross carrier (or pool) scheduling isperformed for various purposes/reasons (e.g., congestion control) (e.g.,when SA transmission and data transmission are performed on differentcarriers (or pools), and when a (rear) part of data (or SA) repetitiontransmission is performed in a different carrier (or pool)), differentPHY formats may be used in the different carriers (or pools) accordingto a pre-defined (or signaled) rule (or information).

Herein, for example, which PHY format (e.g., “RS structure”) used by aV2X UE to transmit (control/data information) on a specific carrier maybe informed (to other V2X UE(s)) through a (new) field on a pre-defined(or signaled) channel (e.g., a PSCCH).

Herein, for example, a PHY format of a channel (e.g., a PSCCH) used totransmit “scheduling/control information (and/or information on a usedPHY format)” may be identically (or commonly) defined for differentcarriers (or pools).

In another example, a V2X UE(s) may be controlled to perform(transmission) resource (re)selection, as below. Hereinafter, an exampleof 1. (Transmission) resource (re)selection operation will be describedwith reference to Table 1, and an example of 2. Transmission resource(re)reservation (or selection) operation by a V2X TX UE(s) will bedescribed with reference to Table 2.

TABLE 1 1. Description about an example of (transmission) resource(re)selection A V2X UE may select a transmission resource in thefollowing method. A UE is assumed to be in a mode for selecting aresource by itself. In the mode, when section/reselection of a resourcefor transmitting a V2X message is triggered, the UE performs sensing andselect/reselect the resource on the basis of the sensing. The UE maytransmit scheduling assignment (SA) indicating the selected/reselectedresource. For example, the UE may be triggered to select/reselect aresource from subframe (or TTI) #n. Then, the UE performs sensingbetween subframe#n − 1 and subframe #n − b (a > b > 0, and a, b arenatural numbers), and selects/reselects a resource for transmitting aV2X message on the basis of a result of the sensing. The a, b may bevalues set commonly for V2X UEs, or may be values set independently foreach V2X UE. Alternatively, when the a, b are values set commonly forV2X UEs, they may be, for example, in a relationship of “a = 1000 + b”.That is, when the UE is triggered to select by itself a resource fortransmitting a V2X message, the UE may perform sensing operation in onesecond (1000 ms = 1000 subframes = 1000 TTI). The UE may consider all SAtransmission decoded from the subframe #n − a to the subframe #n − b.The decoded SA may relate to data transmission in a section from thesubframe #n − a to the subfrmae #n − b, and the decoded SA may considereven data transmitted prior to the subframe #n − a. The UE not havingperformed on sensing on subframe #m (e.g., for the reason of a need oftransmitting a signal on the subframe #m) may exclude subframes #(m +100*k) from resource selection/reselection. Meanwhile, the UE does notperform sensing operation on subframes used by itself to transmit asignal, and skips sensing. After the sensing, the UE selects atime/frequency resource for a PSSCH, that is, a sidelink data channel.The UE may transmit scheduling assignment (SA) on subframe #n + c. C isan integer equal to or greater tha 0, and it may be a fixed value or avariable. The UE may not be required to perform SA transmission (thatis, PSCCH transmission) to subframes whose value of C is smaller thanC_(min). C_(min) may be a fixed value or a value set by a network. TheSA transmitted on the subframe #n + c may indicate associated datatransmitted from subframe #n + d. d may be an integer equal to orgreater than c. Both of c and d may be values equal to or smaller than100. d may be a value equal to or smaller than d_(max). d_(max) may bedetermined dependent upon a priority of UE/data/service type. The UE mayinform whether or not to reuse a signal transmitted on the subframe #n +d for potential transmission of another Transport Block (TB) on subframe#n + e. Herein, e is an integer and in a relationship of d < e. The UEmay explicitly or implicitly inform whether to reuse the above signal. emay be a single value or multiple values. In addition, the UE may informthat a frequency resource for transmitting a signal on the subframe #n +d will be not used after the subframe #n + e. A receiver UE receiving aV2X signal decodes scheduling assignment (SA) transmitted by atransceiver UE transmitting the V2X signal. At this point, it may beassumed that the same frequency resource is reserved in subframe #n +d + P*j (j = i 2*i, . . . , J*i) by the SA. P may be 100. The value of Jmay be implicitly signaled by the SA or may be a fixed value (e.g., 1).The value of i may be explicitly signaled by the SA, or may be a presetvalue or a fixed value. Alternatively, the value of i may be an integerbetween 0 and 10. Meanwhile, if any one of the following conditions issatisfied, reselection of a V2X resource may be triggered. 1. When acounter satisfies an expiration condition, The value of the counter mayincrease at each TB transmission, and, when reselection of all ofsemi-statically selected resources is triggered, the value of thecounter may be reset. The value to be reset may be randomly selectedbetween 5 and 15 at an equal probability. 2. When a TB is not suitablefor the current resource allocation despite use of the maximumModulation and Coding Scheme (MCS), 3. When resource reselection isindicated by an upper layer. Meanwhile, when all PSCCH/PSSCHtransmissions have the same priority, selection/reselection of a PSSCHmay be performed through the following procedure. First of all, allresources is considered selectable, and specific resources are excludedbased on SA decoding and additional conditions. At this point, the UEmay select one of the following two options. The first option isexcluding resources whose DM-RS power received from resources indicatedor reserved by decoded SA and from data resources related to the SA isequal to or greater than a threshold value. The second option isexcluding resources whose energy measured in resources indicated orreserved by decoded SA and in data resources related to the SA is equalto or greater than a threshold value. The UE may select a V2Xtransmission resource from non-excluded resources. For example, the UEmay measure and rank remaining PSCCH resources based on the totalreceived energy, and select sub sets. The UE may compare energy in thecurrently selected resources and energy in the sub sets, and, if theenergy of the selected resources is greater than the energy of the subsets, the UE may select one of the sub sets. The UE may randomly selectone resource from the selected sub set. 2. When a TB is not suitable forthe current resource allocation despite use of the maximum Modulationand Coding Scheme (MCS), 3. When resource reselection is indicated by anupper layer. Meanwhile, when all PSCCH/PSSCH transmissions have the samepriority, selection/reselection of a PSSCH may be performed through thefollowing procedure. First of all, all resources is consideredselectable, and specific resources are excluded based on SA decoding andadditional conditions. At this point, the UE may select one of thefollowing two options. The first option is excluding resources whoseDM-RS power received from resources indicated or reserved by decoded SAand from data resources related to the SA is equal to or greater than athreshold value. The second option is excluding resources whose energymeasured in resources indicated or reserved by decoded SA and in dataresources related to the SA is equal to or greater than a thresholdvalue. The UE may select a V2X transmission resource from non-excludedresources. For example, the UE may measure and rank remaining PSCCHresources based on the total received energy, and select sub sets. TheUE may compare energy in the currently selected resources and energy inthe sub sets, and, if the energy of the selected resources is greaterthan the energy of the sub sets, the UE may select one of the sub sets.The UE may randomly select one resource from the selected sub set. Or,the UE may measure and rank remaining PSSCH resources based on totalreceived energy, and select sub sets. The UE may randomly select oneresource from the sub sets. Or, the UE may measure and rank remainingPSSCH resources based on total reception energy, and select sub sets.The UE may select a resource, which minimizes fragmentation of frequencyresources, from the sub sets. Or, the UE may measure received power of aPSSCH resource indicated by decoded SA, add it up as total receivedpower of subframes, and sort out the subframes according to the totalreception power. The UE randomly select a transmission subframe from aset of available subframes. Then, the UE may randomly select a frequencyfrom a transmission subframe. In the above-described procedure, the UEexcludes a specific resource based on SA and additional conditions, andselects a V2X transmission resource. At this point, when SA and dataassociated with the SA are transmitted on the same subframe, a method ofexcluding a resource based on DM-RS received power of a PSSCH may besupported. That is, it is excluding resources whose PSSCH referencesignal received power (RSRP) received from resources indicated orreserved by decoded SA and from data resources associated with the SA isequal to or greater than a threshold value. Specifically, the PSSCH RSRPis may be defined as a linear average of power distribution of resourceelements (REs) which carry DM-RSs associated with the PSSCH in physicalresource blocks (PRBs) indicated by a PSCCH. The PSSCH RSRP may bemeasured with reference to an antenna connector of the UE. The SA mayinclude a 3-bits PPPP field. The threshold value may be given in theform of a function regarding priority information. For example, thethreshold value may be dependent on priority information of TBs andpriority information of decoded SA. The threshold value may be given ona unit basis of [2 dBm] in a range between [−127 dBm] and [0 dBm], 64threshold values in total may be preset. The UE may decode SA onsubframe #m −+ c in a sensing section, and assume that the samefrequency resource is reserved on subframe #m + d + P*i by the SA. ASdescribed above, P may be a fixed value of 100. i may be selected from arange of [0, 1, . . . , 10], and may be subcarrier-specifically set by anetwork or may be preset. i = o indicates no intention of reserving afrequency resource, i may be set by a 10-bit bitmap or may be set by a4-bit field in SA. When a semi-static resource candidate X collides withresource Y, which is reserved due to SA of a different UE, in periodP*I, and when an exclusion condition is satisfied, the UE may excludethe resource candidate X. I is a value of i which is signaled by SA.When resources remaining after resource exclusion through SA decodingand sensing operation is smaller than 20% of all resources in aselection window, the UE may increase a threshold value (e.g., 3 dB) andexclude a resource again, and this procedure may be performed untilresources remain more than 20% of total resources in the selectionwindow. The total resources in the selection window indicate availableresource candidates that the UE needs to consider. Meanwhile, in theprocedure of selecting a V2X transmission resource after excluding aspecific resource, when the counter reaches 0, the UE may maintain thecurrent resource at a probability of p and reset the counter. That is, aresource may be reselected at a probability of 1 − p. Asubcarrier-specific parameter p may be preset and may be set in a rangeof [0, 0.2, 0.4, 0.6, and 0.8], The UE measures remaining PSSCHresources except for a specific resource, ranks the remaining PSSCHresources on the basis of total received energy, and select a sub set.The sub set may be a set of resource candidates having the lowestreceived energy. The size of the sub set may be 20$ % of total resourcesin a selection window. The UE may randomly select one resource from thesub set. When a single TB is transmitted on a single subframe, the UEmay select M number of consecutive sub-channels, and an average ofenergy measured in each sub-channel may be an energy measurement valueof each resource.

TABLE 2 2. Description about an example of an operation of (re)reserving(or selecting) a transmission resource by a V2X TX UE(s) 2-1. UEprocedure for determining subframes and resource blocks for transmittingPSSCH and reserving resources for sidelink transmission mode 4 Thenumber of sub frames in one set of time and frequency resources fortransmission of PSSCH is given as C_(resel). In this case, if C_(resel)is set, it may be given as [10*SL_RESOURCE_RESELECTION_COUNTER], andotherwise C_(resel) may be set to 1. When the same set of sub-channelsin a subframe t_(m+p) _(rsvp) _(*j) ^(SL) may be determined regardingPSCCH transmissions corresponding to the same slidelink grant. Herein, J= 1, 2, . . . and, with respect to C_(resel) − 1, P_(rsvp), a resourcereservation interval may be determined by upper layers. 2.2. UEprocedure for transmitting the PSCCH Regarding the sidelink transmissionmode 4, a UE may set SCI format 1 as below. IfSL_RESOURCE-RESELECTION_COUNTER is greater than 1, the UE may set aresource reservation field as a resource reservation section determinedby upper layers separated by P_(step). Herein, P_(step) may be 100. Ifnot, the UE set a resource reservation field to 0. 2.3. UE procedure fordetermining the subset for resources to be excluded in PSSCH resourceselection in sidelink transmission mode 4 In response to a request fromupper layers on subframe n, a UE may determine a set of resources to beexcluded from PSSCH transmission according to the following steps. Theupper layers may determine a parameter L_(subCH) corresponding to thenumber of sub- channels used for PSSCH transmission on a subfrrame, aparameter P_(rsvp)_TX corresponding to a resource reservation intervaldetermined by an upper layer, and a parameter prio_(TX) corresponding toa priority transmitted by a UE in SCI format 1. STEP 1) A singlesubframe resource candidate Rx, y relating to PSSCH transmission may bedetermined as the same as a set of sub-channels adjacent to asub-channel x + j on a subframe t_(y) ^(SL). Herein J = 0, . . .L_(subC−) − 1. STEP 2) The UE monitors subframes n − 1001~, n − 1000, n− 999, . . . , n − 2 which are excluded from the UE's transmissionchange. STEP 3) A parameter Th_(a, b) may be set as the same as a valuethat starts by the i-th SL- ThreasPSSCH-RSRP field inSL-ThresPSSCH-RSRP-List-r14. In this case, i = a*8 + b + 1. STEP 4) Aset S_(A) may be reset to a combination of all single frame resourcecandidates. A set S_(B) may be reset to an empty set. STEP 5) When thefollowing condition is satisfied, the UE excludes a subframe subframeresource candidate R_(x, y) from the set S_(A). The UE may receive SCIformat 1 from a subframe t_(y) ^(SL). In addition, a “resourcereservation” field and a “priority” filed in the received SCI format 1may respectively indicate P_(rsvp)_RX and prio_(RX). PSSCH-RSRPmeasurement according to the received SCI format 1 may be greater thanTh_(prio) _(TX,) prio_(RX). The same SCI format 1 estimated to bereceived from the subframe Th_(m+prio) _(step·) _(prio) _(rsvp) _RX maybe determined depending on resource blocks and a set of subframesoverlapping with R_(x, y+P) _(rsvp) _TX_(*J) regarding j = 0, 1, . . . ,C_(resel) − 1 STEP 6) If the number of single subframe resourcecandidates remaining in the set SA is smaller than 0.2 · M_(total), STEP4 may be repeated as the same as Th_(a, b) which has increased by 3 dB.STEP 7) Regarding a single subframe resource candidate R_(x, y)remaining in the set S_(A), a matrix E_(x, y) may be defined as the sameas a linear average of S-RSSI measured in a sub- channel x + k regardingsubframes k = 0, . . . , L_(subCH) − 1 monitored in STEP 2. STEP 8) TheUE may transfer the single subframe resource candidate R_(x, y) alongwith the minimum matrix E_(x, y) from the set S_(A) to a set S_(B). Thisstep may be performed repeatedly. STEP 9) A set Sc may be defined as aset of all single subframe resource candidates not included in the setS_(B).

For example, the following coexistence methods proposes methods in whicha V2X UE(s) effectively performs V2X communication-related “sensingoperation” and/or “resource (re) selection operation” when detectinganother communication (e.g., “DRSC/IEEE 802.11P service”, “(differentnumerology-based) NR eV2X service”) on a specific channel (orband/carrier) according to (the above-described) rule and performing“channel (or band/carrier) switching (or changing) operation”.

Herein, for example, the term “sensing” may be understood as an energymeasurement operation on a pre-defined (or signaled) reference signal(RS) and/or a channel (e.g., DM-RS RSRP of PSSCH (associated with adecoded PSCCH) and/or S-RSSI), or as a decoding operation on apre-defined (or signaled) channel (e.g., PSCCH).

Herein, for example, such (some) coexistence methods may be applicableeven to the case where a V2X UE(S) performs a “channel (or band/carrier)switching (or changing) operation” according to a pre-defined rule (oraccording to a received signaling (or indication) (from a (serving) basestation (or RSU)) since a “congestion level” of a specific channel (orband/carrier), on which V2X communication is being implemented, hasincreased (to be higher than a pre-set (or signaling) threshold value).

[Coexistence Method #2] When performing a “channel (or band/carrier)switching (or changing) operation”, a V2X UE(s) is allowed to randomly(re)select resources (from a “V2X resource pool” on a switched (changed)channel (or band/carrier)) to be used for V2X communication.

Herein, for example, the “channel (or band/carrier) switching (orchanging) operation” may be understood to be a condition for triggering(or performing “(transmission) resource (re)selection”.

Herein, for example, the resources randomly (re)selected according tothe rule may be allowed (to be used only to transmit “Transport Block(TB)” a pre-set (or signaled) number of times (e.g., “1”) after thechannel (or band/carrier) switching (or changing) operation”) not for“reservation” (or “Semi-Persistent Scheduling (SPS)”).

Herein, for example, when the “channel (or band/carrier) switching (orchanging) operation” is implemented, the randomly (re)selected resourcesmay be (exceptionally) allowed for “reservation” (or “SPS”) (for thepurpose of multiple (or pre-set (or signaled) number of times of) “TB”transmission) or may be allowed to be used (or reserved) as a(frequency) resource used for (multiple (or pre-set (or signaled) numberof times of) “TB” transmission in the future.

In another example, a V2X UE(s) may be allowed to (first) perform a“sensing” operation on a switched (or changed) channel (or band/carrier)in a pre-set (or signaled) period of time, and then, based on theresult, (re)select (optimal) resources used for V2X communication.

Herein, for example, the “sensing time section” value (and/or the“PSSCH-RSRP measurement” threshold value on STEP 5 of Section 2.3. ofTable 2 (which may be understood as a “0.2*Mtotal”-related coefficient(or proportion) value on STEP 6 (or 8) of Section 2.3. of Table 2 (e.g.,a proportion value for deriving (or determining) the minimum number ofresources (candidates) (from among total resources (candidates)) toremain (in the SA set) after STEP 8 of Section 2.3. of Table 2 and/or asa proportion value for deriving (or determining the (minimum) number ofresources (candidates) to remain in the SB set after STEP 8 of Section2.3. of Table 2), and/or a “PSSCH-RSRP measurement” increased value(e.g., “3DB”) applicable when the minimum number of resources(candidates) (from total resources (candidates)) to remain in the SA setafter STEP 5 of Section 2.3. of Table 2 is not satisfied, and/or aperiod value used for energy measurement operation (e.g., STEP 8 inSection 2.3. of Table 2)) may be set (or signaled) to be different from(e.g., having a relatively smaller (or greater) value than) (or the sameas) a value (e.g., “1000 MS”) applied (or used) when “channel (orband/carrier) switching (or changing) operation” is not performed.

Herein, for example, the number of limited subframes (of a resourcereservation (interval) period) assumed (or used) for transmissionresource (re)reservation (or selection) (and/or a Cresel value (e.g.,“[10*SL_RESOURCE_RESELECTION_COUNTER]”) in Table 2 Section 2.1), and/ora 1_VALUE (range) value able to be selected (or allowed) on a V2Xresource pool (and/or (V2X) carrier), and/or a P_STEP value, and/or atransmission power-related (OPEN-LOOP) parameter (or value) (e.g., “PO”,“ALPHA”, etc.) may be set (or signaled) differently compared to thosevalues applied (or used) when the channel (or band/carrier) switching(changing) operation” is not performed.

[Coexistence Method #3] When performing a “channel (or band/carrier)switching (or changing) operation”, a V2X UE(s) may (re)select resources(from a “V2X resource pool” on a switched (or changed) channel (orband/carrier)) to be used for V2X communication according to thefollowing (some) rules.

(Example #3-1) Despite a “channel (or band/carrier) switching (orchanging)” operation, if there is no (to-be-transmitted or generated)packet (or message) on a “(low layer) buffer” (and/or “PDCP LAYER”), aV2X UE(s) may (partially) perform a “sensing” operation (on “V2Xresource pool” on a switched (or changed) channel (or band/carrier)).

Herein, for example, a “(partial) sensing” operation may be performeduntil a (to-be-transmitted or generated) packet (or message) exists (orreaches) a “(low layer) buffer” (or until a packet (or message) isgenerated) (or only in a pre-set (or signaled) period of time).

Herein, for example, when such a rule is applied, a V2X UE(s) may lastly(re)select the most suitable (transmission) resource (from a “V2Xresource pool” on a switched (or changed) channel (or band/carrier))based on a result of the “(partial) sensing” operation.

Herein, for example, a V2X UE(s) may (re)select its own (transmission)resource (limitedly) only in a resource (region) where a “(partial)sensing” operation is performed.

Herein, for example, it may be defined such that a “TB”transmission-related (frequency) resource is allowed for “reservation(or “SPS”) only when a “(partial) sensing” operation is performed.

In another example, if “latency” remains a lot (more than a pre-set (orsignaled) threshold value) despite “channel (or band/carrier) switching(or changing)”, a V2X UE(s) may (partially) perform a “sensing”operation (on a “V2X resource pool” on a switched (or changed) channel(or band/carrier)).

(Example #3-2) (In the above (Example #3-1)) Depending on whether or nota pre-set (or signaled) condition is satisfied, a V2X UE(s) may perform(or select) one of (A) resource (re)selection based on a “(partial)sensing” operation and (B) resource (re)selection based on “random”.

Herein, for example, when the following (some) conditions are satisfied,the resource (re)selection based on “random” (or resource (re)selectionbased on a “(partial) sensing” operation) may be performed: otherwise,the resource (re)selection based on the “(partial) sensing” operation(or resource (re)selection based on “random”) may be performed.

(Example #3-2-1) The case where a (newly) generated (orto-be-transmitted) packet (or message) exists on a “(lower layer)buffer” (and/or on a “PDCP layer”) when “channel (or band/carrier)switching (or changing)” is performed.

(Example #3-2-2) The case where “latency” less than a set (or signaled)threshold value remains when “channel (or band/carrier) switching (orchanging)” is performed.

(Example #3-2-3) The case where a resource-related “(reselection)counter” value (re)selected from a “V2X resource pool” on an existingchannel (or band/carrier) when “channel (or band/carrier) switching (orchanging)” is performed (and/or the case where “TB” transmission isperformed (or not performed) a pre-set (or signaled) number of times (orperiod) using a (re)selected (frequency) resource).

(Example #3-3) When a V2X UE(s) performs “channel (or band/carrier)switching (or changing)”, a location of a V2X communication-related(transmission) resource (at least) on a switched (or changed) channel(or band/carrier) may be succeeded (or maintained) identically alocation thereof on an existing channel (or band/carrier) in the casewhere a “(reselection) counter” value relating to a resource(re)selected from a “V2X resource pool” on the existing channel (orband/carrier) is greater (or smaller or equal) than a pre-set (orsignaled) threshold value (e.g., “0”) (and/or in the case where “TB”transmission is not performed (or is performed) a pre-set (or signaled)number of times (or period) using a (re)selected (frequency) resourceagain, and/or in the case where, when the “channel (or band/carrier)switching (or changing)” is performed, a (newly) generated (orto-be-transmitted) packet (or message) exists (or does not exist) (on a“(low layer) buffer (and/or on a “PDCP layer”)), and/or in the casewhere, when the “channel (or band/carrier) switching (changing)” isperformed, less “latency” (or more latency) (than a pre-set (orsignaled) threshold value) remains.

Herein, for example, when such a rule is applied, (some) parametersrelated to (transmission) resource (re)selection on an existing channel(or band/carrier) (e.g., “(reselection) counter”, a number of times (orperiod) “TB” transmission is performed using a (re)selected (frequency)resource, etc.) may be understood to be succeeded to a switched (orchanged) channel (or band/carrier).

Herein, for example, the above rule may be applied limitedly only to thecase where the existing channel (or band/carrier) is identical to V2Xcommunication-related “resource pool configuration (or bandwidth)” onthe switched (or changed) channel (or band/carrier).

For example, in the case where a V2X UE(s) performs “channel (orband/carrier) switching (or changing)” and sets a location of a V2Xcommunication-related (transmission) resource on a switched (or changed)channel (or band/carrier) (re)using a result of sensing on the existingchannel (or band/carrier), the V2X UE(s) may select (or reserve) (themost) suitable resource (based on the result of sensing on the existingchannel (or band/carrier)) by considering only a (V2Vcommunication-related) resource (pool) region in which the existingchannel (or band/carrier) and the switched (or changed) channel (orband/carrier) overlap (on a logic resource region).

Herein, for example, in the case where a V2X UE(s) performs “channel (orband/carrier) switching (or changing)” and sets a location of a V2Xcommunication-related (transmission) resource on a switched (or changed)channel (or band/carrier) (re)using a result of sensing on the existingchannel (or band/carrier), if the corresponding location of the(transmission) resource which has been set ((re)using the result ofsensing on the existing channel (or band/carrier) is (already) occupiedby a different V2X UE(s) on the switched (or changed) channel (orband/carrier) (e.g., this may be understood as the case where the V2XUE(s) has (previously) performed a sensing operation on the switching(or changed) channel (or band/carrier)), (A) only a colliding(transmission) resource may be reselected (and/or randomly selected)and/or (B) only a non-colliding (overlapping) (transmission) resourcemay be used for (V2X message) transmission.

For example, while a V2X UE(s) (having a receiving (or sensing)capability related to a plurality of channels (or bands/carriers))performs a sensing (receiving) operation on the (corresponding)plurality of channels (or bands/carrier) (and/or another communication(e.g., “DSRS/IEEE 802.11P service”, “(different numerology-based) NReV2X service”) detection operation), if another communication isdetected on a channel (or band/carrier) on which the V2X UE(s) iscurrently performing a (V2X message) transmission operation, the V2XUE(s) may select one of the (corresponding) plurality of channels (orbands/carriers) on which the sensing (receiving) operation (and/oranother communication detection operation) is performed (except for thecorresponding channel (or band/carrier), and, may perform a channel (orband/carrier) switching (or changing) operation.

Herein, for example, the V2X UE(s) may first select (A) a channel (orband/carrier) of which a congestion level (and/or a sensed energymeasurement value) is (relatively) low, and/or (B) a channel (orband/carrier) in which resources occupied by the V2X UE(s) is(relatively) less, and/or (C) a channel (or band/carrier) in whichanother communication is not detected, and/or (E) a channel (orband/carrier) having a (relatively) low (or high) index (and/or firstselect a (high (or low) (priority) level) channel (or band/carrier)according to a pre-set (or signaled) (priority) level), or may selectrandomly.

For example, while a V2X UE(s) uses a (pre-set (or signaled)) specificcarrier (or channel/band) for (V2X message) transmission, if a pre-set(or signaled)) different carrier (or channel/band) is determined to havea relatively lower “congestion level” (and/or “load level”) andaccordingly the V2X UE(s) immediately (or quickly) switches to the(corresponding) different carrier (or channel/band), the system maybecome unstable.

Herein, for example, to alleviate the corresponding problem, (A) a timerfor maintaining (V2X message) transmission on an existing carrier (orchannel/band) (before (“congestion level” (and/or “load level”)-based)carrier (or channel/band) switching is applied) may be set (orsignaled), and/or (B) switching to a (relatively low “congestion level”(and/or “load level”) different carrier (or channel/band) may beperformed only when a “congestion level difference” between an existingcarrier (or channel/band) and the different carrier (or channel/band)(and/or “load level difference”) exceeds a pre-set (or signaled)threshold value (e.g., which can be understood as a kind of (“congestionlevel” (and/or “load level”)-related) “hysteresis”).

For example, a V2X UE(s) assumes that there are a resource (RES_L), forwhich “RAT” is set (or signaled) with a (relatively) low priority, and aresource (RES_H) for which “RAT” is set (or signaled) with a(relatively) high priority (see Table 3).

Herein, for example, while a V2X UE(s) performs V2X communication on“RES_H”, when the V2X UE(s) considers switching (or offloading) to“RES_L” because a (measured) (“RES_H” related) “congestion level” valueis greater than a pre-set (or signaled) threshold value (CL_RSC_H)(e.g., “CL_RSC_H” can be regarded a threshold value associated with“RES_H”) (actual) switching (from “RES_H” to “RES_H”) may be allowedonly when the “RES_L” related (measured) “congestion level” value issmaller than a pre-set (or signaled) threshold value (CL_RSC_L) (e.g.,“CL_RSC_L” can be regarded as a threshold value associated with“RES_L”).

Herein, for example, “CL_RSC_H” and “CL_RSC_L” may be set (or signaled)to be different values (e.g., “CL_RSC_H>CL_RSC_L”).

For example, a V2X UE(s) may perform a “congestion level” (and/or “loadlevel”) measurement operation (and/or “another communication” (e.g.,“DSRC/IEEE 802.11P service”, “(different numerology-based) NR eV2Xservice”) (and/or “other RAT”) detection operation), not in a V2Xresource pool (designated in the form of “carrier(or cell)-specificnetwork (pre)configuration”), but even in a (pre-set (or signaled)(external) resource region.

Herein, for example, if an ((external) resource region-related)“congestion level” (and/or “load level”) measurement is high, it may bedetermined that “another communication” (and/or “other RAT”) exists.

Herein, for example, the corresponding ((external) resourceregion-related) “congestion level” (and/or “load level”) measurement(and/or “another communication” (and/or “other RAT” detection) may beimplemented in a pre-set (or signaled) (additional) sub-channel (in an(external) resource region) and/or implemented in the entire bands (inan (external) resource region).

Herein, for example, a (“congestion level” (and/or “load level”)measurement-related) (S-RSSI) measurement operation may be performedwithin a V2X resource(s) in any V2X resource pool.

Herein, for example, the corresponding (“congestion level” (and/or “loadlevel”) measurement-related) (S-RSSI) measurement operation may beperformed in the form of “(V2X) pool-specific” (or “(V2X) pool-common),and a region other than the (V2X) pool may be measured additionally.

Herein, for example, the measurement operation (in the V2X resource(s))in the above (some) rules may be performed in a (V2X) TX pool (and/or(V2X) RX pool) (on a corresponding carrier).

For example, when a V2X TX UE(s) performs switching of (“V2Xcommunication” (and/or “V2X message TX operation”) related) carrier (orchannel/band/pool) (according to a pre-set (or signaled) rule (or(priority) level), the V2X TX UE(s) may (in advance) signal (orbroadcast) the carrier (channel/band/pool), on which the V2X performsswitching, to a (neighboring) V2X RX UE(s) through a pre-defined channel(e.g., “PSCCH (or PSSCH)” and/or “PSBCH”).

Herein, for example, a (specific) carrier (or channel/band/pool) onwhich a channel for the purpose is transmitted may be pre-set (orsignaled) (in the form of “UE-common”).

For example, Table 3 shows a method by which “V2X communication” and“another communication (e.g., “DSRC/IEEE 802.11P service”, “(differentnumerology-based) NR eV2X service”) coexist efficiently.

TABLE 3 3. Example of a method for allowing “V2X communication” and“another communication” to coexist efficiently Proposal 1: LTE SL V2Vdesign for coexistence with Dedicated Short-Range Communications (DSRC)needs to consider coexistence with NR V2X. That is, LTE SL V2V designfor coexistence with NR V2X needs to be considered. 3.1. Availablesolutions distinguishable in phase Proposal 2: RAN1 specificationsupport may not be necessary for options of “geographical location anddatabase” and “GNSS timing-based time share between systems” 3.2.Detection of a different RAT Proposal 3: A LTE UE may detect existenceof a different RAT when high energy is observed in a resource having noLTE transmission. The “resource having no LTE transmission” may be aresource set as implicit resources or may be a resource where an LTCsignal is not found. Proposal 4: Even when there is high load on LTE SLV2V, a solution may be needed to guarantee a transmission chance of IEEE802.11p In order to secure detectability, transmitting by a UE adetection signal whenever transmitting PSCCH/PSSCH on a subframe may beused as a reference. One method is to use the first symbol and/or thelast symbol in frequency resources of a corresponding PSCCH/PSSCH(including a probability of using some of those symbols). Herein,Automatic Gain Control (AGC) may be performed on the first symbol, andTX/RX switching and uplink (UL) TX timing advantage absorbing may beperformed on the last symbol. Hereinafter, two options of a LTE SL V2Vdetection signal will be described. FIG. 8 illustrates an example of aLTE SL V2V detection signal using time repetition of a short sequence.Referring to FIG. 8, in the first option, a short sequence may berepeated on the first symbol and/or the last symbol. An intendedoperations of a detection device is delaying a time domain receivedsignal as long as a length of the sequence, and using so-called “delaycorrelation” of a received signal correlated with a next receivedsignal. In this operation, the device does not detect the sequenceitself but is able to distinguish a specific repetition pattern of asignal in a time domain. Accordingly, the device does not need to knowthe exact sequence used by a transmitter, and this is an advantage overa detection device using a different RAT. FIG. 9 illustrates an exampleof an LTE SL V2V detection signal using sequence matching in a frequencydomain. According to FIG. 9, in the second option, a detection device isable to match each sequence of each frequency resource. Since atransmission bandwidth of PSSCH is possibly not informed to thedetection device, a size of a resource block (RB) of a detection signalmay be, for example, fixed to one sub-channel size so as to use the samesequence in every UE while maintaining a single carrier. In order tosupport AGC on the first symbol and maintain the same coverage, PowerSpectral Density (PSD) needs to be boosted in detection signal wtransmission which uses some of a PSSCH transmission bandwidth. Proposal5: If a predetermined signal is used for inter-RAT detection, a UE needsto transmit a new LTE SL signal on the first symbol and/or the lastsymbol of every subframe that transmits PSCCH/PSSCH. Herein, AGC needsto be guaranteed on the first symbol, and TX/RX switching and timingadvance absorbing of UL TX need to be guaranteed on the last symbol.3.3. Use of resources potentially shared with a different RAT Adetect-and-vacate operation assumes a prioritized access to a resource.In other words, when a RAT with a determined priority is detected, a RATfor stopping a different RAT from using a resource is prioritized.Accordingly, it may be necessary to define when a UE performstransmission with a high priority on a resource to be potentially usedby a different RAT. In addition, whether or not two RATs are allowed tohave the same priority may be further discussed, and, for example, the“First Come First Served (FCFS)” principle may be adapted. Proposal 6:it may be assumed that, in a detection-and-vacate operation, differentRATs in a given resource set have different priorities. If alow-priority RAT (e.g., RAT A) detects a RAT (e.g., RAT B) from aspecific resource set of a low priority, the low-priority RAT (e.g., RATA) may stop transmission. Regarding this, the question is which resourceis used for transmission of RAT A, and especially, whether apredetermined level of a waiting time or reliability requirements areneeded for this transmission. In this case, stopping transmission is notreasonable, and thus, it may be possible to basically assume that theRAT A is a different resource set Y having a high priority. Thus, interms of a RAT, the resource set Y may be used for basic resources, anda resource set X may be a kind of an auxiliary resource set optionallyused for offload. The RAT A may use a resource set X only whenoffloading is necessary. Otherwise, the RAT A may interfere with RAT Bbecause inter-RAT detection is not perfect. In addition, it is necessaryto prevent use of unnecessary multicarrier as much as possible, byconsidering a limitation on the number of carriers to be used by each UEand overhead/latency of the case of switching and alignment of carriersby a UE. This may mean that a UE does not use a resource set of alow-priority RAT when there is no congestion problem in a resource setof a high-priority RAT. Proposal 7: In a detect-and-vacate operation,each RAT may be assumed to have the highest-priority resource set. Onlywhen the RAT detects congestion in the highest- priority resource set,the UE may use a different resource. A resource set in which LTE SL V2Vhas a low priority level may be set in multiple carriers. In this case,a receiver UE may need to know which carrier is used by a transmitter UEfor the purpose of offloading. To support this operation, the UE maybroadcast information on a transmission carrier to adjacent UEs. Tosupport alignment used by carriers over the UEs, a carrier having thefirst priority from among the carriers may be first considered as atransmission carrier. When time for completely monitoring a carrierswitched by the UE is not allowed, random resource selection discussedfor V2P or limited resource detection may be considered a fallbackoperation. On the other hand, when each UE has a multi-carrier receivingfunction and already monitors carrier candidates, this fallbackoperation may not be necessary. Thus, an assumed subcarrier capacity maybe discussed first. Proposal 8: when a detect-and-vacate operation isperformed using multiple carriers, how to align transmission carriersamong UEs needs to be discussed. 3.4. Coexistence of inter-RAT in thecase of V2P In the case of V2P, a P-UE transmission and V-UE receptionscenario is prioritized during SI step. However, if a mechanism ofdetection-based coexistence of RATs is used even for V2P, it isnecessary to consider a limited P-UE RX capability. One option is toimplement each P-UE to detect any other RAT before transmission, butthis may require more battery consumption and an RX function of PC5carrier. There is a limitation that, even though partial sensingoperation, a P-UE is not able to detect any other RAT in a subframewhich is not monitoring. To solve this problem, supporting an eNB may beconsidered. Each V-UE may report detection of a different RAT inaddition to its location information to an eNB. Accordingly, the eNB mayforward the information to a P-UE, and the P-UE may determinetransmission on the basis of the location information of the V-UE fromthe forwarded information. Selectively, the eNB may activate/deactivatea resource pool for P-UEs in a region on the basis of reports fromV-UEs. Proposal 9: If a detect-and-vacate operation is performed in thecase of V2P, a solution for allowing a P-UE to recognize a different RATmay be needed. V-UE reporting and eNB forwarding may be considered. 3.5.The above-described proposals may be summarized as below Proposal 1:Regarding an LTE SL V2V design for coexistence with Dedicated Short-Range Communication (DSRC), expansion about coexistence with NR V2Xneeds to be considered. Proposal 2: For the options “geographicallocation and data base” and “GNSS timing- based time haring betweensystems”, RANI specification support may not be needed. Proposal 3: Whenhigh energy is observed in a resource having no LTE transmission, an LTEEE may detect a different RAT. The “resource having no LTE transmission”may be a resource set along with implicit resources or a resource inwhich an LTE signal is not found. Proposal 4: Even when there is highload for LTE SL V2V, a solution may be necessary to guarantee atransmission chance of IEEE 802.11p. Proposal 5: When a predeterminedsignal is used for inter-RAT detection, a new LTE SL signal needs to betransmitted from the first symbol and/or the last symbol in everysubframe on which a UE transmits PSCCH/PSSCH. Herein, AGC needs to beguaranteed in the first symbol, and TX/RX switching and UL TX timingadvance absorbing needs to be guaranteed on the last symbol. Proposal 6:In a detect-and-vacate operation, different RATs in a given resource setare assumed to have different priorities. Proposal 7: In adetect-and-vacate operation, each RAT may be assumed to have thehighest-priority resource set. When the RAT detects congestion in thehighest priority set, a UE may be consider using a different resourceset. Proposal 8: When a detect-and-vacate operation is performed usingmultiple carriers, how to align transmission carriers among UEs needs tobe discussed. Proposal 9: When a detect-and-vacate operation isperformed in the case of V2P, a solution for allowing a P-UE torecognize a different RAT may be needed. V-UE reporting and eNBforwarding may be considered.

Even examples of the above-described coexistence method may be includedas one of methods of implementing the present invention, and thus, it isobviously that it can be regarded as a kind of coexistence method. Inaddition, the above-described coexistence methods may be implementedindependently and may be implemented in the form of a combination(integration) of some coexistence methods. For example, the presentinvention describes the coexistence methods based on a 3GPP LTE systemfor convenience of explanation, but the range of a system to which acoexistence method is applicable may expand to systems other than a 3GPPLTE system.

For example, the coexistence methods of the present invention may beapplicable even for D2D communication. Herein, for example, the D2Dcommunication indicates that a UE performs communication directly withother UE using a radio channel, and, herein, for example, the UEindicates a user's terminal, but a network device such as a base stationmay be regarded as a kind of UE when transmitting/receiving a signalaccording to a communication method between UEs.

In addition, for example, the coexistence methods of the presentinvention may be applicable limitedly only to MODE 2 V2X operation(and/or MODE 1 V2X operation). In addition, for example, the coexistencemethods of the present invention may be applicable limitedly only to aV-UE(s) (or P-UE(s)) (and/or a V2X UE(s) provided with a (dedicated) RX(or TX) chain about a V2X carrier (or channel/band)).

Hereinafter, the present invention will be described.

In the following methods, a UE may be a UE having a limited capability.For example, a UE may be a UE having a limited RX (or TX) chain/circuitcapability (and/or a UE having a limited battery capability (orduration/time/consumption). For example, a UE may be a UE which includesonly one receiver (or transceiver) not to be able to simultaneouslyreceive (or transit) a signal for WAN communication at a first frequencyand a signal for V2X communication at a second frequency. The UE may bea pedestrian UE (Pedestrian UE: P-UE which is carried out by apedestrian) which has relatively huge constraints in terms of hardwareimplementation costs/increase in complexity/battery consumption(compared to a UE installed at a vehicle (Vehicle-UE: V-UE)).

Hereinafter, there is proposed a method by which the UE efficientlyperforms a V2X message transmission (or reception) operation on a V2Xsub-carrier or V2X resource pool (a subcarrier/resource pool for whichV2X communication is set).

Hereinafter, for convenience of explanation of the proposed method, forexample, a P-UE #K is assumed to have single TX circuit (RXchain/circuit) capability and two TX circuits (TX chain/circuit)capability.

In addition, P-UE #K is assumed to perform wide area network (WAN) DL/ULcommunication on WAN DL/UL subcarrier #X (which can be understood assubcarriers for which WAN DL/UL communication is set) and perform a V2Xmessage transmission (or reception) operation (together) on V2Xsubcarrier #Y. However, the proposed methods of the present inventionmay be applicable not just to this case, but also to other various cases(e.g., the case of requiring more than a RX (or TX) circuit capabilityof a V2X UE).

The P-UE #K may be understood to have no “dedicated RX (or TX)chain/circuit)” on the V2X subcarrier #Y on which V2X communication isimplemented. That is, it may be understood that only the “TX(or RX)chain/circuit” exists on the V2X subcarrier #Y.

A “transmission resource collision avoidance operation (that is, sensingoperation)” between different V2X UEs is more helpful to improve V2Xcommunication performance, compared to a random method of randomlyselecting/reselecting a transmission resource by V2X UEs.

The sensing operation may be performed (A) through decoding of“scheduling assignment (SA) channel (e.g., PSCCH)”, and/or measurement(e.g., “PSSCH-RSRP”) on a pre-defined channel/reference signal (RS whichis, for example, “DM-RS”) on a “DATA channel (e.g., PSSCH)” associatedwith the (corresponding) decoded PSCCH, and/or (B) energy measurement(e.g., “S-RSSI”).

Hereinafter, for example, the term such as a subcarrier/band/channelused herein may be understood to indicate a resource pool.

<Proposed Method #1>

When performing a V2X message transmission operation on V2X subcarrier#Y, P-UE #K (having a limited RX circuit capability) does not use (orswitch) a reception circuit (RX chain/circuit) used for a WAN downlinkreception operation (WAN DL carrier #X) (regardless of whether a sensingoperation is set) but may (always) (re)select a transmission resource(on V2X subcarrier #Y) for V2X message transmission by using a randommethod.

For example, a V2X message may be (periodically) transmitted based on aperiod value (which is determined on an upper layer (of a UE)) (and/ortransmitted based on a (periodic) resource (re)selected (or reserved)based on the corresponding period value). Herein, for example, when(re)selecting (or reserving) (transport block (TB)-related)(data/scheduling assignment) transmission resource, P-UE #K may performs(re)selection (or reservation) limitedly on remaining subframes, exceptfor a subframe to which a (TB-related) (data/scheduling assignment)transmission resource (re)selected (or reserved) belongs, at a previous(period (or transmission resource (re)selection (or reservation)) time(whereby a half-duplex problem can be alleviated).

For example, when (re)selecting (or reserving a transmission resource),the P-UE #K may transmit a V2X message by selecting a specificsubframe(s) from (re)selected (or reserved) resource candidates composedof 100 subframes (which is assumed to be indexed from 0 to 99). Ifselecting the N-th subframe (from the (re)selected (or reserved)resource candidates) at the previous transmission resource (re)selection(or reservation) time, the P-UE #K may (randomly) select a specificsubframe from remaining subframes, except for the N-th subframe (in the(re)selection (or reservation) resource candidates), at a nexttransmission resource (re)selection (or reservation) time.

Herein, for example, the P-UE #K may perform a V2X message transmissionoperation using “UU interface” or a WAN uplink (when a sensing operationis set). Such an operation may be understood to be switching between PC5and UU (or the WAN uplink).

<Proposed Method #2>

The P-UE #K (having a limited RX circuit capability) may assume that a“sensing gap (or sensing resource) or reception gal (or receptionresource) or a partial sensing gap (or partial sensing resource)” of apreset or signaled pattern (e.g., a “bitmap/period/offset”) exists on atime/frequency resource and/or V2X message transmission (atime/frequency resource prior to a (scheduling assignment) period (ortime) for performing a resource (re)selection (or reservation)operation). Herein, for example, the term “sensing gap or reception gap”may indicate a partial sensing gap (which is be set as the same in thefollowing). Herein, for example, the “sensing gap” may indicate aresource on which a UE needs to perform sensing to (re)select (orreserve) a resource (e.g., a subframe) used to transmit a V2X signal,and, in this aspect, the sensing gap may be indicated as a sensingresource. Similarly, the “reception gap” may be indicate a resource onwhich the UE needs to receive (or decode) a signal (or channel) toperform the sensing (and/or a resource for PSSCH-RSRP/S-RSSImeasurement), and, in this aspect, the reception gap may be indicated asa reception resource. In addition, the “partial sensing gap” mayindicate a (some) resource set for the sensing, and, in this aspect, thepartial sensing gap may be indicated as a partial sensing resource.

On the sensing gap (or resource) (or the reception gap (orresource)/partial sensing gap (or resource), which is set as the same inthe following), the P-UE #K may switch (or use) its own receptioncircuit used for a WAN downlink reception operation (WAN DL subcarrier#X) and or perform a sensing operation (or a partial sensing operation).The sensing operation may include at least one of (1) an operation ofacquiring information on occupied resources by performing a decodingoperation on scheduling assignment channels transmitted by a differentV2X terminal or 2) an operation of acquiring information on resourceshaving aggressive interference or resources occupied by a different V2Xterminal through an (energy) measurement operation (e.g., PSSCH-RSRP,S-RSSI) on a defined channel/reference signal.

Through such a sensing operation, transmission resource avoidance with adifferent V2X terminal is possible.

FIG. 10 shows an example of a V2X transmission resource (re)selection(or reservation) in a partial sensing operation according to <ProposedMethod #2>.

Referring to FIG. 10, a UE (P-UE, which is set as the same in thefollowing) may determine (or trigger) (re)selection (or reservation) ofa resource for V2X signal transmission (depending on whether apredefined condition is satisfied). For example, suppose that(re)selection (or reservation) of a resource for V2X signal transmissionis determined (or triggered) on subframe #m. In this case, the UE may(re)select (or reserve) the resource for V2X signal transmission in asubframe section from subframe #m+T1 to subframe #m+T2. The subframesection from subframe #m+T1 to subframe #m+T2 will be referred to as aselection window in the following. The selection window may be, forexample, composed of 100 consecutive subframes.

In the selection window, the UE may select at least Y number ofsubframes as resource candidates. That is, the UE may need to considerat least the Y number of subframes in the selection window to beresource candidates. The value of Y be a preset value or may be a valueset by a network. However, how to select the Y number of subframes inthe selection window may be the question of UE implementation. That is,if the value of Y is, for example, 50, which 50 subframes from the 100subframes of the selection window may be selected by the UE. Forexample, the UE may select 50 subframes with odd subframe numbers or 50subframes with even subframe numbers from among the 100 subframes.Alternatively, the UE may select 50 subframes according to a randomrule.

Meanwhile, to (re)select (or reserve) a specific subframe, for example,subframe #N(SF #N), from among the Y number of subframes as a V2Xtransmission subframe capable of transmitting a V2X signal, the UE mayneed to sense at least one subframe linked with or associated with thesubframe #N. A (whole) subframe section defined for sensing is referredto as a sensing window and may be, for example, composed of 1000subframes. That is, a sensing window may be 1000 ms or one second. Forexample, a UE may be able to sense subframes corresponding to subframe#N-100*k (herein, K may be a set of respective elements within a rangeof [1, 10] and may be a value which is preset or which is set by anetwork) within a sensing window.

FIG. 10 illustrates an example in which the value of k is {1, 3, 5, 7,10}. That is, a UE may sense subframes #N-1000, #N-700, #N-500, #N-300,and #N-100, estimate/determine whether subframe #N is being used by adifferent V2X UE (and or whether there is interference (equal to orgreater than a pre-set (or signaled) threshold value) on the subframe#N), and lastly select the subframe #N based on the result. Since a P-UEis sensitive to battery consumption compared to a V-UE, the P-UEperforms partial sensing: that is, the P-UE senses some of subframes ina sensing window, rather than all of the subframes.

FIG. 11 shows an example of (re)determining (or selecting/reserving) aV2X transmission subframe (or resource) according to <Proposed Method#2>.

Referring to FIG. 11, a UE receives pattern information used todetermine a (partial) sensing pattern (S191). The pattern informationmay be provided by a network through an RRC (or SIB) message or thelike.

The following table shows an example of pattern information.

TABLE 4 -- ASN1START SL-P2X-SensingConfig-r14 ::=        SEQUENCE {  minNumCandidateSF-r14     INTEGER (1 . . 13),  gapCandidateSensing-r14        BIT STRING (SIZE 10)) } -- ASN1STOP

In the above table, “minNumCandidateSF” indicates the minimum number ofsubframes required to be included in possible resource candidates. Asdescribed above, a UE needs to consider at least Y number of subframesin a selection window as resource candidates, and, in this case,“minNumCandidateSF” may indicate the value of Y.

“gapCandidateSensing” indicates a specific subframe to be sensed whenthe specific subframe is considered resource candidates. As describedabove, when specific subframes, for example, subframe #N(SF #N), isselected as a resource candidate from among the Y number of subframes,it is necessary to sense subframes corresponding to #N-100*k in asensing window, and, in this case, the “gapCandidateSensing” mayindicate the value of K using a 10-bits string.

For example, in the case where the value of K is {1, 3, 5, 7, 10}, itmay be expressed as ““1001010101”.

The UE senses some subframes which is determined, based on the patterninformation, from the subframes in the sensing window (S192). That is,the UE performs partial sensing. The partial sensing has been alreadydescribed in detail with reference to FIG. 10.

The UE selects a specific subframe in the selection window as a V2Xtransmission subframe based on the sensing (S193).

FIG. 12 illustrates a method of communication among a P-UE, a V-UE, anda network according to <Proposed Method #2>. Herein, for example, FIG.12 assumes the case where a P-UE transmits a V2X signal to the V-UE,but, generally, the V2X signal transmitted by the P-UE may target notjust the V-UE, but other entities (e.g., P-UE, V-UE, (UE-TYPE) RSU,etc.).

Referring to FIG. 12, a network provides a (sensing) pattern to the P-UE(S201). The pattern information has been already described withreference to Table 4.

The P-UE performs partial sensing based on (sensing) patterninformation, and selects a V2X transmission subframe on the basis of theresult (S202).

The P-UE transmits a V2X signal to the selected V2X transmissionsubframe (S203).

<Proposed Method #3>

(A P-UE having a limited RX circuit capability, for example) P-UE #K mayreport (to a network through a WAN UL) information on a sensing gap (orresource), a reception gap (or resource), or a partial sensing gap (orresource of its preferred form or pattern. Herein, for example, thecorresponding information on the sensing gap (or resource), thereception gap (or resource), or the partial sensing gap (or resource)may be in the form of a bitmap and/or the form indicating aperiod/offset value (of the sensing gap (or resource) (or reception gap(or resource)/partial sensing gap (or resource))).

A preferred sensing gap (or resource) (or a reception gap (orresource)/partial sensing gap (or resource) form/pattern may includesome time/frequency resource regions which has a relatively low energymeasurement value (and/or a “congestion level” value) after P-UE #Kperforms a measurement (or sensing) operation (on a pre-set or signaledtime/frequency resource section).

<Proposed Method #4>

(In the case where the above Proposed Method #3 is applied) when sensinggap (or resource) (or reception gap (or resource) or partial sensing gap(or resource)) pattern (received from a base station) does not cover thewhole (or more than a pre-set (or signaled) (threshold) proportionvalue) (previous) time/frequency resource (or pool) region necessary fora sensing operation (relating to a pool (or resource) on which a V2Xmessage transmission operation is to be performed) (e.g., when thecorresponding sensing gap (or resource) (or reception gap (orresource)/partial sensing gap (or resource) covers only some resources(or subframes) in a sensing window), the corresponding V2X messagetransmission operation may be performed according to the following rule.

Herein, for example, when the V2X message transmission operation isperformed on V2X transmission resource pool #J (associated withscheduling assignment pool (or period) #J), a sensing operation on thecorresponding V2X transmission resource pool #J may be performed on aprevious time frequency resource V2X transmission resource pool #(J-1)(e.g., which is associated with scheduling assignment/period #(J-1)). Asdescribed above, a sensing operation based on a sensing gap (orresource) (or reception gap (or resource)) may be understood as a“partial sensing operation”.

(Example #4-1) On a sensing gap (or resource) (or reception gap (orresource or partial sensing gap (or resource), which will be set as thesame in the following) (received from a base station), it is possible toperform an operation of avoiding a transmission resource collision witha different V2X UE by using only acquired sensing information (e.g.,information on a resource occupied by the V2X UE, and information on aresource having aggressive interference).

For example, (if a sensing gap (or resource) (or reception gap (orresource)/partial sensing gap (or resource) does not cover the whole(single) repetition period (or sensing window) in the case another UErepeatedly use a resource at a predetermined interval), a P-UE may(re)select (or reserve) its optimal transmission resource only in aresource which is sensed using the sensing gap (or resource) (or thereception gap (or resource)/partial sensing gap (or resource)).

For example, in the case of (re)selecting (or reserving) a resourcehaving the lowest energy, it may be limited to (re)selecting (orreserving) a resource having the lowest energy from among resourcesbelonging to a sensing gap (or resource) (or reception gap (or resource)or partial sensing gap (or resource)).

For example, in the case of figuring out a resource occupied by a UEthrough decoding of a scheduling assignment channel of a different UE,it may be limited to (re)selecting (or reserving) only a “data resource”which is allowed to be scheduled in a scheduling resource belonging to asensing gap (or resource) (or reception gap (or resource) or partialsensing gap (or resource)).

When (re)selecting (or reserving) a (TB related) (data or schedulingassignment, which will be set as the same in the following) transmissionresource at the current transmission resource (re)selection (orreservation) (period) time, P-UE #K may limitedly perform (re)selection(or reservation) in remaining subframes, except for a subframe to whicha (TB related) (data or scheduling assignment) transmission resource(re)selected (or reserved) at a previous (re)selection (or reservation)(period) time belongs. In doing so, it is possible to alleviate ahalf-duplex problem in a transmission resource (re)selection (orreservation) operation environment based on imperfect sensinginformation). The half-duplex problem means that, because a UE is notcapable of transmitting and receiving a signal at the same time, whenthe UE uses repeatedly use the same resource (e.g., a frequencyresource) for signal transmission/reception, the UE is not able torepeatedly perform signal reception/transmission.

FIG. 13 illustrates an example of a method of (re)selecting (orreserving) a V2X transmission resource according to Example #4-1.

Referring to FIG. 13, at a first transmission resource (re)selection (orreservation) time (or period), a UE may select a first subframe 223 in afirst selection window 222. Linked Subframes to be sensed in order toselect the first subframe 223 are expressed as sensing resources in thefirst sensing window 221.

At a second transmission resource (re)selection (or reservation) time(or period, the UE may select a second subframe 226 in a secondselection window 224. At this point, the second subframe 226 is asubframe which does not overlap a subframe 227 at the same position (ororder) as that of the first subframe 223 (in the selection window). Thatis, the second subframe 226 is selected from among remaining subframesexcept for the subframe having the same location/subframe order (ornumber) as that of the first subframe 223 in the second selectionwindow. Linked subframes to be sensed in order to select the secondsubframe 226 are expressed as sensing resources in the second sensingwindow 224.

According to this method, different resources are selected from thefirst selection window and the second selection window, and thus, it ispossible to alleviate the half-duplex problem.

A sensing operation on an excluded subframe (or resource) and a linkedsensing resource may be omitted, and/or the excluded subframe (orresource) and the linked sensing resource may not be included in asensing gap (by reporting relevant information to a base station by P-UE#K).

FIG. 14 illustrates a method of (re)selecting (or reserving) V2Xtransmission resource according to Example #4-1.

Referring to FIG. 14, in a second selection window, a UE selects asecond subframe, which does not overlap a first subframe selected in thefirst selection window, as a resource candidate (S211).

The UE senses subframes linked/associated with the second subframe inthe second sensing window (S212).

The UE may select the second subframe as a V2X transmission subframe onthe basis of the sensing result (S213).

(Example #4-2) For example, a transmission resource (re)selectionoperation may be performed using a pre-defined or signaled other method,e.g., a random method.

In another example, a V2X message transmission operation may beperformed using “UU interface” or WAN uplink. Such an operation may beunderstood as switching between PC5 and UU (or WAN uplink).

(Example #4-3) If not receiving sensing gap (or resource) (or receptiongap (or resource) or partial sensing gap (or resource)) patterninformation from a base station), P-UE #K may (re)select (or reserve) atransmission resource using a pre-defined or signaled other method (orfallback method) (e.g., a random method) (even though a sensingoperation is set). Alternatively, a V2X message transmission operationmay be performed using “UU interface” (or WAN uplink).

[Proposed Method #5] if a P-UE performs a sensing operation for a longtime, it may lead to deterioration of WAN downlink reception performance(due to WAN DL RX chain/circuit switching) and/or may be not good interms of battery consumption. Alternatively, if a (partial) sensingoperation is performed only on a fixed (or (semi-)static) time/frequencyresource region for a short time or a limited period of time, it maydeteriorate accuracy of energy sensing and transmission resourcecollision avoidance performance. Considering the above, (partial)sensing operation-related parameters, for example, a length of a sectionon which the (partial) sensing operation is to be performed (sensingduration), and a (partial) sensing pattern (which indicates a form (orpattern)/period/offset of the sensing operation, and which can beprovided in a bitmap form) may be set to be subject to “(time) hopping”and/or “randomization” according to a pre-defined rule.

“(time) hopping (pattern)” and/or “randomization (pattern)” may berandomized between different V2X UEs. For example, the randomization maybe performed by a function which is pre-defined based on at least one ofinput parameters such as ID of a transmitter UE, ID of a receiver UE, a(resource/pool) (period) index on which a V2X message transmissionoperation is performed, and a scheduling (resource/pool) (period) index.

Meanwhile, (although having a RX chain/circuit capability,) a UE mayhave a limited TX chain/circuit capability about a plurality ofsubcarriers. In this case, the UE may sense, out of resources belongingto a pre-defined or signaled “TX gap”, an associated sensing resource(which is associated with a resource in the TX gap) and limitedly(re)select its optimal transmission resource on the basis of the result.

The TX gap may be understood as a resource region in which V2X messagetransmission has a relatively high priority compared to WAN ULtransmission.

In this case, a V2X UE may (re)select (or reserve) a resource(s) notbelonging to the TX gap to be used for transmission of a V2X message,and therefore, it is possible to alleviate the problem of omission (ordropping) of the transmission of the V2X message due to overlapping withthe WAN UL transmission (on the same (or different) subcarrier) (and/orallocation of transmission power with a low priority).

The P-UE #K having the limited TX chain/circuit capability may report anetwork of TX gap information of a preferred form (or pattern) (e.g.,“bitmap/period/offset”) (through a WAN UL).

The preferred TX gap form (or pattern) may include (some)(time/frequency) resource regions which has a relatively low (energy)measurement value (and/or “congestion level” value) after the P-UE #Kperforms a measurement (or sensing) operation (on a pre-set (orsignaled) (time/frequency) resource (section)).

Alternatively, the TX gap may be applied commonly to subcarriers thatperform V2X communication. When the TX gap is set (or applied) (commonlyapplied to the subcarriers), it is possible to alleviate “V2Xcommunication performance degradation”, which occurs becausetransmission power is distributed to “WAN UL transmission” on the basisof a high priority when “WAN UL transmission” and “V2X messagetransmission” occur at the same time or when “WAN UL transmission” and“V2X message transmission” partially overlap with each other in a timedomain.

In other words, when WAN UL transmission” and “V2X message transmission”(partially or entirely) overlap with each other on differentsubcarriers, it may be understood that transmission power is allocated(or distributed) to the V2X message transmission with a priorityrelatively higher than that of the WAN UL transmission. If this rule isapplied, it is possible to alleviate degradation of performance of V2Xcommunication (or Public Safety (PS) communication) which occurs becauselow transmission power is allocated (or distributed) to V2X messagetransmission.

Alternatively, from the perspective of one V2X UE, when “WAN ULtransmission” and “V2X message transmission” occur at the same time orwhen “WAN UL transmission” and “V2X message transmission” partiallyoverlap with each other in a time domain, if a section is set as a TXgap, transmission power may be allocated (or distributed) to the V2Xmessage transmission on the basis of a priority relatively higher thanthat of the WAN UP transmission while a pre-defined or signaled minimumtransmission power value may be guaranteed to the WAN UP transmission.If this rule is applied, it is possible to guarantee the minimumperformance of the WAN UP communication.

Hereinafter, suppose that a V2X UE capable of (partially) performing asensing operation (based on scheduling assignment decoding/energymeasurement), for example, a V-UE and/or a P-UE, is TYPE #A UE. That is,the TYPE #A UE is a UE capable of performing (partial) sensing. Inaddition, suppose that a V2X UE (e.g., a P-UE) incapable of (partially)performing a sensing operation (based on scheduling assignmentdecoding/energy measurement) is TYPE #B UE. That is, the TYPE #B UE is aUE incapable of performing (partial) sensing.

Meanwhile, there may be a variety of types of a V2X transmissionresource pool.

FIG. 15 illustrates an example of a type of a V2X transmission resourcepool.

Referring to FIG. 15(a), V2X transmission resource pool #A may be aresource pool on which only (partial) sensing is allowed. In the V2Xtransmission pool #A, a UE needs to select a V2X transmission resourceafter performing (partial)sensing, wherein random selection is notallowed. The V2X transmission resource selected through the (partial)sensing is semi-statically maintained in a predetermined period, asillustrated in FIG. 15(a).

For a UE to perform V2X message transmission on the V2X transmissionresource pool #A, a base station may set a (scheduling assignmentdecoding/energy measurement-based) sensing operation to be (partially)performed. This may be understood that “random selection” of atransmission resource on the V2X transmission resource pool #A is notallowed and that (only) “(partial) sensing”-based transmission resourceselection is performed (or allowed). Such setting may be done by thebase station.

Referring to FIG. 15(b), V2X transmission resource pool #B may b aresource pool on which only random selection is allowed. In the V2Xtransmission resource pool #B, a UE may not perform (partial) sensingbut may randomly select a V2X transmission resource from a selectionwindow. Herein, for example, in a resource pool on which only randomselection is allowed, a selected resource may be set (or signaled) notto be semi-statically reserved, unlike in the resource pool on whichonly (partial) sensing is allowed.

To perform a V2X message operation on the V2X transmission resource pool#B, a base station may set to perform a (scheduling assignmentdecoding/energy measurement-based) sensing operation. This may beunderstood that (only) “random selection” of a transmission resource isperformed (or allowed) and/or “(partial) sensing”-based transmissionresource selection is not allowed on the V2X transmission resource pool#B.

Meanwhile, although not illustrated in FIG. 15, there may be a resourcepool on which both (partial) sensing and random selection are allowed. Abase station may inform that a V2X resource can be selected (by the UE'simplementation) using either of the partial sensing and the randomselection from the resource pool.

FIG. 16 illustrates an example of a method of selecting a V2X pool whenresource pools of multiple types exist.

Referring to FIG. 16, a UE receives type information indicating a typeof a resource pool (S300).

The following table is an example of the type information.

TABLE 5 -- ASN1START SL-P2X-ResourceSelectionConfig-r14 :: =    SEQUENCE{   partialSensing-r14     ENUMERATED {true}  OPTIONAL, -- Need OR  randomSelection-r14   ENUMERATED {true}   OPTIONAL  -- Need OR } --ASN1STOP

In the above table, “partialSensing” indicates that partial sensing isallowed for a UE to select a resource in a corresponding resource pool.“randomSelection” indicates that a UE is allowed to randomly select in acorresponding resource pool. That is, type information indicates amethod by which a UE is able to select a V2X transmission resource in aspecific resource pool, thereby informing a type of the specificresource pool (e.g., a resource pool in which only partial sensing-basedtransmission resource selection is allowed, a resource pool in whichonly random selection-based transmission resource is allowed, and aresource pool in which both partial sensing and random selection-basedtransmission resource selection is allowed).

The UE may perform at least one of random selection-based resourceselection or partial sensing-based resource selection in the resourcepool, on the basis of the type information (S310).

For example, a base station may allow TYPE #A UE through a pre-definedsignaling (the type information) to perform transmission resourceassignment/scheduling in the V2X transmission resource pool #A based ona (scheduling assignment decoding/energy measurement-based) sensingoperation, and to perform a (scheduling assignment decoding/energymeasurement-based) sensing operation-omitted (or random selection-based)transmission resource assignment/scheduling and V2X message transmissionoperation in the V2X transmission resource pool #B (or based onrandom-selection).

Even though a UE is capable of performing a (scheduling assignmentdecoding/energy measurement-based) sensing operation, it is possible toallow the UE to perform (not just (scheduling-assignment decoding/energymeasurement-based) sensing operation-based transmission resourceassignment/scheduling and a V2X message transmission operation (on theV2X transmission resource pool #A) a (scheduling assignmentdecoding/energy measurement-based) sensing operation-omittedtransmission resource assignment/scheduling, and V2X messagetransmission operation (e.g., a random selection technique) (on the V2Xtransmission resource pool #B). Herein, for example, ((however) if a V2Xtransmission resource pool required to be subject to (schedulingassignment decoding/energy measurement-based) sensing operation exist inthe V2X transmission resource pools), the TYPE #A UE may be set to((necessarily) use a V2X transmission resource pool on which a(scheduling assignment decoding/energy measurement-based) sensingoperation is required to be performed/applied and/or) perform a(scheduling assignment decoding/energy measurement-based) sensingoperation-based transmission resource assignment/scheduling, V2X messagetransmission operation (on the V2X transmission resource pool #A).

In other words, it may be understood to restrict (or prohibit) use of aresource (V2X transmission resource pool) for a V2X UE having arelatively pool sensing-related capability to a V2X UE having arelatively good sensing-related capability. And/or, it may be understoodthat, since the V2X UE having a relatively good sensing-relatedcapability and the V2X UE having a relatively good sensing-relatedcapability use (or shape) the same V2X transmission resource pool, it ispossible to prevent performance of V2X communication of the V2X terminalhaving the relatively good sensing-related capability from degrading dueto transmission resource collision.

Through pre-defined signaling, the base station may inform the TYPE #BUE of whether to allow “random selection” of a transmission resourceonly in the V2X transmission resource pool #B or of whether to allow“random selection” of a transmission resource even in the V2Xtransmission resource pool #A.

It may be set (or signaled) such that, after “(partial) sensing”-basedselection of a transmission resource in the V2X transmission resourcepool #A, the selected transmission resource is maintained (or reserved)for a predetermined period of time. And/or, it may be set/signaled suchthat, after “random selection” of a transmission resource in the V2Xtransmission resource pool #B, the selected transmission resource is notmaintained (or reserved) for a predetermined period of time. And/or, itmay be set (or signaled) such that a V2X UE having a “(partial) sensing”capability (and/or reception circuit capability) and (having switched(barrowed) a reception chain” used for WAN DL reception) (e.g., a P-UE)selects a transmission resource based on “random selection” and thenmaintains (or reserves) the selected transmission resource for apredetermined period of time.

Each V2X transmission resource pool is set/signaled to be shared fortransmission between which types of V2X UEs. For example, a specificresource pool may be set (or signaled) to be shared between a V-UE and aP-UE, but a different resource pool may be set(or signaled) to be usedonly by the V-UE (or P-UE). And/or, whether a (P-UE related) resourcepool for which “random selection” is allowed partially or entirelyoverlaps with a “(partial) sensing”-based resource pool (used by theV-UE) (e.g., when the “random selection”-allowed resource pool the“(partial) sensing”-based resource pool (both) overlap, a correspondingresource pool may be understood as a resource pool for which “randomselection”-based resource selection and “(partial) sensing”-basedresource selection are both (or simultaneous) allowed.

Whether or not random selection is allowed for a specific resource pooland/or a V2X subcarrier or whether sensing-based selection is allowedtherefor may be explicitly indicated using type information, asdescribed above, but they may be implicitly implied with a range valueof a preset or signaled specific parameter (which is I_VALUE).

For example, when a parameter of a specific resource pool (and/or (V2X)subcarrier) is set (or signaled) not to select (or allow) remainingvalues except “0”, the specific resource pool may be understood as aresource pool used only by a UE (e.g., a P-UE) which performs “randomselection” of a transmission resource.

Meanwhile, it may be set (or signaled) such that a specific pool isshared for transmission between a V-UE and a P-UE and/or that a “randomselection” allowed (P-UE related) resource pool and a “(partial)sensing”-based resource pool (used by a V-UE) partially or entirelyoverlap with each other. In this case, a (P-)UE performing “randomselection” may need to maintain (or reserve) a transmission resource,“randomly selected” in a corresponding resource pool, for apredetermined period of time. Or, (when it is not set (or signaled) suchthat a specific pool is shared for transmission between a V-UE and aP-UE and/or that a “random selection” allowed (P-UE related) resourcepool and a “(partial) sensing”-based resource pool (used by a V-UE)partially or entirely overlap with each other), a (P-)UE performing“random selection” may not need to maintain (or reserve) a transmissionresource, “randomly selected” in a corresponding resource pool, for apredetermined period of time.

FIG. 17 illustrates an example of an operation that randomly selects aresource in a (partial) sensing-allowed resource pool.

For various reasons, a UE is able to select a V2X transmission resource312 through random selection in a (partial) sensing-allowed resourcepool. For example, when a (partial) sensing-allowed resource pool and arandom selection-allowed resource pool overlap with each other (and/orwhen random selection and (partial sensing) are both allowed in aspecific pool), a UE may select a V2X transmission resource throughrandom selection in the (partial) sensing-allowed resource pool.

In this case, the UE may semi-statically reserve resources 313 havingthe same frequency as that of the V2X transmission resource 312. Thatis, the UE repeatedly reserve a randomly selected resource over aspecific section with a predetermined period. When the resource poolfrom which the resource is selected overlaps with the (partial)sensing-allowed resource pool even though the UE actually selecting aresource though random selection (and/or when the resource pool fromwhich the resource is selected allows both random selection and(partial) sensing), it is understood that the UE performs a similaroperation as that of a UE(performing (partial) sensing operation) in the(partial) sensing-allowed resource pool.

Meanwhile, for a V2X UE (e.g., a P-UE) capable of performing a(scheduling assignment decoding/energy measurement-based) sensingoperation only within a pre-set (or signaled) limited time (orfrequency) resource section (or region), the same rule (or method) as arule implemented by TYPE #A UE (or TYPE #B UE) may be applied.

Alternatively, the TYPE #A UE may not (or may) perform a (schedulingassignment decoding/energy measurement-based) sensing operation in orderto perform a V2X message transmission operation in the V2X transmissionresource pool #B.

For example, a P-UE(s) in (A) “limited sensing_UE” form and/or (B) “TYPE#B_UE” form and/or (C) “limited RX chain/circuit” form (or ‘no RXchain/circuit” form) (e.g., when there is no “dedicated RXchain/circuit” on V2X carrier #Y on which V2X communication isimplemented (or when there is only “TX chain/circuit)) is hard to(efficiently (or quickly)) know whether a neighboring (or adjacent)other V2X UE(s) (e.g., “V-UE(s)”) performs “its (sidelink) service(related V2X message TX operation)” and/or “public safety (PS) service(related V2X message TX operation)”.

Accordingly, it is possible to solve (or alleviate) such a problem byapplying the following (some) methods.

For example, the following (some methods) may be (widely) used even fora P-UE(s) having the above-described “(limited) capability (orchain/circuit))” (e.g., the “limited sensing_UE” form, “TYPE #B_UE”form, and “limited RX chain/circuit” form (or the form which has only“no RX chain/circuit” form or “TX chain/circuit”)) to discover (ordetect) whether “another communication (e.g., “DSRC/IEEE 802.11Pservice”, “(different numerology-based) new RAT (NR) eV2X service”)exists in a short distance on the same channel (or band/carrier).

Herein, for example, when finding (detecting) that “anothercommunication” exists (in a distance close to the same channel (orband/carrier) (on which V2X communication is implemented)), the P-UE(s)may efficiently coexist (or (collision) avoid) according to the above“proposed coexistence methods (especially what is described in <Methodfor allowing “V2X communication” and “another communication” tocoexist>).

Hereinafter, with reference with drawings, there will be provided moredetailed description about a method by which a P-UE, that is, (A) a UEhaving an insufficient (or limited) sensing capability (e.g., theabove-described “limited sensing UE”), or (B) a UE having no sensingcapability (e.g., the above-described “TYPE #B_UE”, or (C) a UE having alimited RX chain/circuit (e.g., the above-described “limited RXchain/circuit”) because of no “dedicated RX chain/circuit” on V2Xcarrier #Y, on which V2X communication is implemented, finds (ordetects) another communication being implemented on a V2X (Vehicle to X)carrier, determines a V2X message transmission resource on the basis ofthe detection result, and then transmits a V2X message on thetransmission resource.

FIG. 18 is a flowchart of a method by which a UE having a limited RXcapability transmits a V2X message according to an embodiment of thepresent invention.

Referring to FIG. 18, a UE may receive information indicating thatanother communication is implemented (or detected) on a V2X (Vehicle toX) carrier (S1010). In this case, the UE having a limited capability ofdetecting the implementation of the another communication may be a UEhaving a limited sensing capability, a UE having no sensing capability,or a UE having no reception chain dedicated to the V2X resource, and theUE may be a P-UE as described above.

Herein, the UE may receive, from (A) other V2X UEs or (B) a basestation, information indicating that another communication isimplemented (or detected) on the V2X (Vehicle to X) carrier. In thiscase, the information indicating that another communication isimplemented (or detected) on the V2X (Vehicle to X) carrier may beinformation indicating a type of a sidelink service being performed onthe V2X resource. In addition, the information indicating that anothercommunication is implemented (or detected) on the V2X (Vehicle to X)carrier may be information indicating that a service being performed onthe V2X resource is a PS (public safety) service. In this case, theinformation indicating that another communication is implemented (ordetected) on the V2X (Vehicle to X) carrier may be informationindicating whether communication based on a radio access technology(RAT) different from a RAT of the V2X communication is implemented onthe V2X communication.

More specifically,

[Proposed Method #6] (A) A different V2X UE(s) (which is located around(or close to) a P-UE(s)) (e.g., “V-UE(s)”) and/or (B) a (serving) basestation may inform (through a pre-set (or signaled) channel) (to theP-UE(s)) information about a “type (or content) of an ITS service” whichis (currently) operating (or detected) and/or “whether or not it is PS(or non-PS) service” (and/or whether or not “another communication(e.g., “DSRC/IEEE 802.11P service”, “(different numerology-based) NReV2X service”) exists), etc.

Herein, for example, this rule may be useful when it is hard for aP-UE(s) to discover the corresponding relevant information as“(sidelink) synchronization signal (SLSS)” (e.g., when “type (ordescription) of an ITS service” and/or “whether or not it is PS (ornon-PS) service” is mapped to “SLSS sequence (or ID)” (and/or whendifferent “SLSS sequence (or ID)” is used for each service (orcommunication)) (and/or when these information is signaled through“PSBCH” (e.g., a specific (reserved) field on the “PSBCH”)), and or whenthere is no “sidelink (dedicated) RX chain/circuit”. Herein, forexample, the term “SLSS” may be understood as “PSSS” (or “SSSS”).

[Proposed Method #7] For example, when “service type (orkind/description) (information)” (e.g., information on “ITS servicetype” and/or “whether or not it is PS (or non-PS) service”) is mapped to“SLSS sequence (or ID)”, (A) a different V2X UE(s) (which is locatedaround (or close to) a P-UE(s)) (e.g., “V-UE(s)”) and/or a (serving)base station may inform (through a pre-set (or signaled) channel) (to aP-UE(s)) information on the detected “SLSS sequence (or ID)”.

Then, on the basis of the information, the UE transmits a V2X message(S1020). Herein, transmitting the V2X message on the basis of theinformation may include determining a transmission resource for the V2Xtransmission message on the basis of the information, and transmittingthe V2X message on the transmission resource. Herein, when anothercommunication is implemented on the V2X resource, the V2X UE switchesthe transmission resource for the V2X message to a V2X resourcedifferent from the V2X resource, and transmits the V2X message on theswitched different V2X resource. The UE may transmit the V2X message onthe switched different V2X resource for a preset period of time, and theswitched different V2X resource may be a subframe other than a subframeused in a TB previously transmitted by the UE.

More specifically,

For example, (in the case where [Proposed Method #7] (and/or [ProposedMethod #6]) is applied) a P-UE(s) may perform an attempt to detect “SLSS(sequence (or ID)) (or PSBCH)” after conducting “wake-up” only on apre-set (or signaled) “sidelink synchronization (or PSBCH) resource(s)”(and/or perform “sensing” operation (for detection (or discovery) ofanother communication”) only in pre-set (or signaled) (time (orfrequency) resource) (some) sections (e.g., which can be understood as akind of “partial sensing” operation) (and/or perform “sensing” operation(for detection (or discovery) of “another communication”) on a (time (orfrequency)) resource (region (or section)) prior to (or just before) aresource selected (or reserved) by itself for V2X message TX (or itstransmission operation (time)) (or prior to a pre-set (or signaled)(time (or timing)) offset value (since its transmission operation(time))) (and/or discover information on “type (or description) of anITS service” which is (currently) operating (or detected) and/or“whether or not it is PS (or non-PS) service” (and/or whether or not“another communication (e.g., “DSRC/IEEE 802.11P service”, “(differentnumerology-based) NR eV2X service” exists), etc.)

Herein, for example, “when another communication” is detected, a rulemay be defined for the P-UE(s) (A) to stop “V2X communication” on anexisting pool (or carrier/channel/band) (and/or “V2X message TXoperation”) and/or (B) to (change a pool (or carrier/channel/band), onwhich “V2X communication” is being implemented, according to apre-defined (or signaled) rule (priority) and/or) perform “V2Xcommunication” on a (corresponding changed) different pool (orcarrier/channel/band) (for a pre-set (or signaled) predetermined periodof time) (and/or “V2X message TX operation”).

In addition, for example, (in the case where [Proposed Method #7](and/or [Proposed Method #6]) is applied) when transmitting (orreporting), to a (serving) base station, information on “type (ordescription) of an ITS service” which is discovered (or detected) and(currently) operating, and/or “whether or not it is “PS (or non-PS)service”, and/or whether or not “another communication (e.g., “DSRC/IEE80211P service”, “(different numerology-based) NR 2 V2X service”)exists, a different V2X UE(s) (e.g., “V-UE(s)) (which is located arounda P-UE(s)) may transmit the information together (additionally) with“its location information” (and/or “information on a location at whichthe corresponding information is discovered”) (and/or a resource pool(or carrier/channel/band) (index) (information) in which(“location-based resource pool (TDM (or FDM)) separation is set (orsignaled)) “another communication (and/or “ITS service” and/or “PS (orNon-PS) service”) is detected.

Herein, for example, the base station may inform the P-UE(s) (which ison a (reported) close (or the same) location (or region)) of thecorresponding information (through a pre-defined signal (e.g., through(WAN) DL (or PDSCH)). Herein, for example, the (serving) base stationhaving received the information (from a V-UE(s)) instruct a P-UE(s)located on a (close or same) location (or region) (and/or pool (orcarrier/channel/band)) where “another communication is detected” toperform “activation/deactivation” of a (related) resource pool, and/orto stop “V2X communication” (and/or “V2X message TX operation”), and/orto switch to a different carrier (or channel/band/pool) according topre-set (or signaled) rule (or priority).

Herein, in another example, when receiving corresponding information(from a (serving) base station), a P-UE(s) may consider (compare) its(current) location (and/or a pool (or carrier/channel/band) on which the“P-UE(s)” (currently) performs V2X message TX operation) so as to decide(or determine) whether to maintain (or stop) a V2X message TX operationand/or whether to perform “V2X communication” (and/or “V2X message TXoperation”) on (the changed) different resource (or channel/band) (for apre-set (or signaled) predetermined period of time) according to apre-defined (or signaled) rule (or a priority). Herein, for example, theP-UE(s) does not need to (directly) make an attempt t detect “SLSS(sequence (or ID)) (or PSBCH)”. Herein, for example, the term “SLSS” maybe understood as “PSSS” (or “SSSS”).

In yet another example, in the case of a P-UE(s) having theabove-described a “(limited) capability (or chain/circuit)” (e.g., the“limited sensing UE” form, “TYPE #B UE” form, and “limited RXchain/circuit” form (or the form which has only “no RX chain/circuit”form or “TX chain/circuit”)), when the P-UE(s) performs “partialsensing” operation to detect (or discover) “another communication”(e.g., “DSRC/IEEE 802.11P service”, “(different numerology-based) newRAT (NR) eV2X service”) (in a pre-set (or signaled) (time (or frequency)resource) section), an (adjacent) different V2X UE(s) (e.g., “V-UE(s))(and/or a (serving) base station (or RSU)) may omit (V2Xcommunication-related) channel/signal transmission in the (pre-set or(signaled)) “partial sensing” (time (or frequency)) resource section (inorder to increase a probability of detecting “another communication”when the “partial sensing” operation” is performed).

In yet another example, (A) a type (or kind) of sensing operation (e.g.,“partial sensing”) that a P-UE(s) performs (having a limited RX (or TX)circuit capability) performs may be set (or signaled), and/or (B) a“SLSS transmission (or reception (or monitoring)) (performing)condition” may be set (or signaled) depending on whether or not randomselection (of a transmission resource) is performed (without sensingoperation).

In yet another example, in the case of a P-UE(s) (having a limited RX(or TX) circuit capability), the following (some) parameters may be set(or signaled) differently (or independently), compared with a V-UE(s).

(Example #1) The limited number of resources (with a resourcereservation (interval) period) assumed (or used) for transmissionresource (re)reservation (or selection) (and/or a proposed coexistencemethod (of the present invention): Cresel value in Section 2.1. of Table2 (e.g., “[10*SL_RESOURCE_RESELECTION_COUNTER]”)).

(Example #2) A V2X message priority (e.g., which may be set (orsignaled) with a relatively low (or high) priority), and/or a“PSSCH-RSRP measurement” threshold value on the proposed coexistencemethod (in the present invention): STEP 5 of Section 2.3. of Table 2(which may be understood as a “0.2*Mtotal”-related coefficient (orproportion) value on the proposed coexistence method (in the presentinvention): STEP 6 (or 8) of Section 2.3. of Table 2 (e.g., a proportionvalue for deriving (or determining) the minimum number of resources(candidates) (from among total resources (candidates)) to remain (in theSA set) after the proposed coexistence method (in the presentinvention): STEP 8 of Section 2.3. of Table 2 and/or as a proportionvalue for deriving (or determining the (minimum) number of resources(candidates) to remain in the SB set after the proposed coexistencemethod (in the present invention): STEP 8 of Section 2.3. of Table 2)(and/or a “PSSCH-RSRP measurement” increased value (e.g., “3 DB”)applicable when the minimum number of resources (candidates) (from totalresources (candidates)) to remain in the SA set after the proposedcoexistence method (in the present invention): STEP 5 of Section 2.3. ofTable 2 is not satisfied, (and/or a period value used for sensingoperation (e.g., the proposed coexistence method (in the presentinvention): STEP 5 of Section 2.3. of Table 2) (and/or energymeasurement operation (e.g., the proposed coexistence method (in thepresent invention): STEP 8 in Section 2.3. of Table 2). Herein, forexample, (that is,) the above-described example of signaling a (partial)sensing pattern of a P-UE by a network may be applicable.).

(Example #3) A I-VALUE (range) value and/or a P_STEP value which areselectable (or allowable) on a V2X resource pool (and/or (V2X) carrier)

(Example #4) A transmission ower-related (open-loop) parameter (orvalue) (e.g., “PO”, “ALPHA”, etc), and/or a V2X resource pool (orcarrier).

In another example, with reference to the following Table 6, “V2Xmessage transmission operation” (and/or “(transmission) resourceselection (or reservation) operation” of a P-UE(s) (having a limited RX(or TX circuit capability) may be efficiently supported.

TABLE 6 4. Example of a method of efficiently supporting “V2X messagetransmission operation” of a P-UE(s) (having a limited RX (or TX)circuit capability) (and/or “(transmission) resource selection (orreservation) operation”) 4.1. Precondition for random resource selectionby P-UE According to the present invention, P-UE including every P-UEhaving no sidelink Rx capability is able to support every posibility ofusing random selection. If the P-UE selects random selection, only apool where the random selection by the P- UE is allowed may be used forthe random selection. Whether a pool where the random selection by theP-UE is allowed to overlap with a different pool may depend on networkconfiguration. A possibility of setting pools where random selection byP-UEs is allowed may be supported. According to the present invention, apossibility for a P-UE to use partial sensing in a sub set of a subframeis supported. Partial sensing by a P-UE may be on the basis of V2Vsensing-based resource selection. In this case, resource selectionaccording to partial sensing by the P-UE may be similar to V2Vsensing-based resource selection. In the case of a P-UE having asidelink Rx function, whether or not partial sensing support isessential may be considered. 4.2. Method for supporting random resourceselection in V2P The current sidelink TX mode 4 is based on resourcereservation (that is, using the same time/frequency resource withrespect to several TB transmissions). Random resource selection by aP-UE will skip a sensing procedure, and thus, whether or not a randomlyselected resource is maintained for a specific period of time needs tobe considered. Applying reservation operation to the random resourceselection may have an advantage and a disadvantage, as below. Advantage:Although a P-UE does not perform detection, a resource reserved by theP- UE may be monitored by a V-UE and it is possible to avoid collisionin resource selection by the V-UE. Disadvantage: When a P-UE selects anon-preferred resource (e.g., a resource used by an adjacent UE or aresource experiencing strong in-band emission from transmission by adifferent UE. The advantage and disadvantage of applying resourcereservation to random selection depend on whether or not P-UEtransmission and V-UE transmission share the same pool. When a randomselection-allowed resource pool does not overlap with a resource poolused for V-UE transmission, no UE is able to take an advantage ofresource reservation, and thus, there is no advantage of applying theresource reservation. Therefore, random selection without resourcereservation needs to be supported in the present invention. For this,whether or not it is necessary to additionally support random selectionthrough resource reservation may be considered. Proposal 1: At leastrandom selection without resource reservation may be supported in thepresent invention. For this, whether or not it is necessary toadditionally support random selection through resource reservation maybe considered. In addition, how resource reselection is performed in arandom resource selection procedure may be considered. To avoidconsistent selection of an unsuitable resource, it is necessary to allowa P-UE to change a resource (that is, selecting a different resourceother than an existing selected resource) in the reselection procedure.More specifically, the P-UE may exclude a subframe used in transmissionof a previous TB, and thus, the impact of in-band emission between TBtransmissions may be randomized. Proposal 2: A P-UE may exclude asubframe used in transmission of a previous TB, and thus, the impact ofin-band emission may be randomized through TB transmission. A TXcapability of the P-UE may be considered as well. Since the P-UE is ableto transmit one message every second, the usage rate of a transmissionchain on a PCC5 carrier for V2P may be 0.2% at the maximum. Thus, whenit is necessary for every P- UE to have a transmission chain dedicatedfor V2P transmission, it may unnecessarily increase costs for UEimplementation. Similarly to 3GPP Rel-12/13 D2D, a ProSe gap is used forP-UE transmission and thus a chain used for UL transmission may beborrowed temporally. Proposal 3: A P-UE may temporally switch atransmission chain used for UL transmission to be used as an SLtransmission chain. 4.3. Conclusion Proposal 1: At least randomselection without resource reservation may be supported in the presentinvention. For this, whether or not it is necessary to additionallysupport random selection through resource reservation may be considered.Proposal 2: A P-UE may exclude a subframe used in transmission of aprevious TB, and thus, the impact of in-band emission between TBtransmissions may be randomized. Proposal 3: A P-UE may temporallyswitch a transmission chain used for UL transmission to be used as an SLtransmission chain.

Hereinafter, for convenience of explanation, the above-describedembodiments will be described with flowcharts. Hereinafter, forconvenience of explanation, the same description applicable redundantlyto the following drawings will be omitted. That is, the above-describedembodiments may be applicable even to the following embodiments.

FIG. 19 is a flowchart of a method for transmitting a V2X message by aUE having a limited RX capability, according to another embodiment ofthe present invention.

Referring to FIG. 19, a UE may receive, from a different V2X UE,information indicating that another communication is implemented (ordetected) on a V2X carrier (S1110). In this case, the different V2X UEmay be a V-UE.

For example, as described above, receiving the information indicatingthat another communication is implemented (or detected) on a V2X carriermay be providing (to a P-UE(s)) (through a pre-set (or signaled)channel) information on “type (or description) of an ITS service” whichis (currently) operating (or detected) and/or “whether or not it is PS(or non-PS) service” (and/or whether or not “another communication(e.g., “DSRC/IEEE 802.11P service”, “(different numerology-based) NReV2X service” exists), etc. Detailed description of this embodiment isthe same as described above and thus it is herein omitted.

Next, on the basis of the information, the UE may determine to transmita V2X message (S1120).

For example, on the basis of the information, a rule may be defined forthe P-UE(s) (A) to stop “V2X communication” on an existing pool (orcarrier/channel/band) (and/or “V2X message TX operation”) and/or (B) to(change a pool (or carrier/channel/band), on which “V2X communication”is being implemented, according to a pre-defined (or signaled) rule(priority) and/or) perform “V2X communication” on a (correspondingchanged) different pool (or carrier/channel/band) (for a pre-set (orsignaled) predetermined period of time) (and/or “V2X message TXoperation”). Detailed description about this example is the same asdescribed above, and thus, it is herein omitted.

In addition, for example, in the case of a P-UE(s) (having a limited RX(or TX) circuit capability), (some) parameters may be set (or signaled)differently (or independently), compared with a V-UE(s). Detaileddescription about this example is the same as described above, and thus,it is herein omitted.

In addition, for example, it is possible to efficiently support “V2Xmessage transmission operation” (and/or “(transmission) resourceselection (or reservation) operation” of a P-UE(s) 9 having a limited RX(or TX) circuit capability). Detailed description about this example isthe same as described above, and thus, it is herein omitted.

Then, the UE may transmit the V2X message on the determined transmissionresource (S1130). A specific example in which the UE transmits the V2Xmessage on the determined transmission resource is the same as describedabove.

FIG. 20 is a flowchart of a method of transmitting a V2X message by a UEhaving a limited RX capability, according to another embodiment of thepresent invention.

Referring to FIG. 20, a base station may receive, from a V2X UE(different from a P-UE) information indicating that anothercommunication is implemented (or detected) on a V2X carrier (S1210). Inthis case, as described above, the different V2X UE may be a V-UE.

For example, as described above, receiving the information indicatingthat another communication is implemented (or detected) on a V2X carriermay be providing (to a P-UE(s)) (through a pre-set (or signaled)channel) information on “type (or description) of an ITS service” whichis (currently) operating (or detected) and/or “whether or not it is PS(or non-PS) service” (and/or whether or not “another communication(e.g., “DSRC/IEEE 802.11P service”, “(different numerology-based) NReV2X service”) exists), etc. Detailed description of this embodiment isthe same as described above and thus it is herein omitted.

In addition, for example, when transmitting (or reporting), to a(serving) base station, information on “type (or description) of an ITSservice” which is discovered (or detected) and (currently) operating,and/or “whether or not it is “PS (or non-PS) service”, and/or whether ornot “another communication (e.g., “DSRC/IEE 80211P service”, “(differentnumerology-based) NR 2 V2X service”) exists, a different V2X UE(s)(e.g., “V-UE(s)) (which is located around a P-UE(s)) may transmit theinformation together (additionally) with “its location information”(and/or “information on a location at which the correspondinginformation is discovered”) (and/or a resource pool (orcarrier/channel/band) (index) (information) in which (“location-basedresource pool (TDM (or FDM)) separation is set (or signaled)) “anothercommunication (and/or “ITS service” and/or “PS (or Non-PS) service”) isdetected. Detailed description about this example is the same asdescribed above, and thus, it is herein omitted.

The UE (which is a UE other than the different V2X UE, for example, aP-UE) may receive, from a base station, the information indicating thatanother communication is implemented (or detected) on a V2X carrier(S1220). That is, the UE may receive, from the base station, forwardedinformation indicating that another communication is implemented (ordetected) on a V2X carrier transmitted by the different V2X UE.Alternatively, the UE may receive, from the base station, informationindicating that another communication is implemented (or detected) on aV2X carrier generated by the base station.

For example, as described above, receiving the information indicatingthat another communication is implemented (or detected) on a V2X carriermay be providing (through a pre-set (or signaled) channel) (to aP-UE(s)) information on “type (or description) of an ITS service” whichis (currently) operating (or detected), and/or “whether or not it is “PS(or non-PS) service”, and/or whether or not “another communication(e.g., “DSRC/IEE 80211P service”, “(different numerology-based) NR 2 V2Xservice”) exists. Detailed description about this example is the same asdescribed above, and thus, it is herein omitted.

Then, on the basis of the information, the UE may determine whether totransmit a V2X message (S1230).

For example, on the basis of the information, a rule may be defined forthe P-UE(s) (A) to stop “V2X communication” on an existing pool (orcarrier/channel/band) (and/or “V2X message TX operation”) and/or (B) to(change a pool (or carrier/channel/band), on which “V2X communication”is implemented, according to a pre-defined (or signaled) rule (priority)and/or) perform “V2X communication” on a (corresponding changed)different pool (or carrier/channel/band) (for a pre-set (or signaled)predetermined period of time) (and/or “V2X message TX operation”).Detailed description about this example is the same as described above,and thus, it is herein omitted.

In addition, for example, in the case of a P-UE(s) (having a limited RX(or TX) circuit capability), (some) parameters may be set (or signaled)differently (or independently), compared with a V-UE(s). Detaileddescription about this example is the same as described above, and thus,it is herein omitted.

In addition, for example, it is possible to efficiently support “V2Xmessage transmission operation” (and/or “(transmission) resourceselection (or reservation) operation” of a P-UE(s) having a limited RX(or TX) circuit capability). Detailed description about this example isthe same as described above, and thus, it is herein omitted.

Then, the UE may transmit the V2X message on the determined transmissionresource (S1240). A specific example in which the UE transmits the V2Xmessage on the determined transmission resource is the same as describedabove.

In the case of PS service-related V2X transmission performed by a V2X UE(which moves relatively fast), WAN transmission may not be alwaysprioritized over V2X transmission.

Regarding this, how to perform V2X transmission when WAN transmissionand V2X transmission overlap in a time domain will be described withreference to drawings.

FIG. 21 is a flowchart of a V2X transmission method according to anembodiment of the present invention when WAN transmission and V2Xtransmission overlap in a time domain.

According to FIG. 21, when V2X transmission and WAN transmission overlapin a time domain, a UE may determine whether or not the V2X transmissionand the WAN transmission are performed on the same carrier (S1310). Inthis case, the UE may be the above-described V2X UE.

Then, the UE may perform the V2X transmission on the basis of thedetermination (S1320). More specifically, there will be provideddetailed description about (A) a method for efficiently determining V2Xtransmission power by the UE when V2X transmission and WAN (UL)transmission (partially or entirely) overlap in a time domain ondifferent carriers and/or (B) a method of prioritizing V2X transmission(which overlaps with WAN (UL) transmission in a time domain on the same(and/or different) carrier) over the WAN (UL) transmission.

(A) Method for efficiently determining V2X transmission power by the UEwhen V2X transmission and WAN (UL) transmission (partially or entirely)overlap in a time domain on different carriers

FIG. 22 schematically illustrates an example in which V2X transmissionand WAN (UL) transmission (partially or entirely) overlap in a timedomain on different carriers.

As illustrated in FIG. 22, a UE may perform V2X transmission on a V2Xcarrier having a frequency f0 at a time t0, and the UE may perform WANtransmission on a WAN carrier having a frequency f1 at the time t0.

When sidelink transmission by a UE on a subframe overlaps ULtransmission by the UE in terms of time, the UE needs to adjust sidelinktransmission power to prevent transmission power from exceeding PCMAX inan overlapping part.

Generally, according to D2D operation, when WAN TX and SL TX overlap ondifferent carriers in terms of time, WAN TX may be prioritized over SLTX in terms of power allocation.

In other words, in the case of the D2D operation, when WAN TX and the SLTX are performed at the same time on different carriers or at anoverlapping time, a UE may allocate more power to the WAN TX (than theSL TX). However, as described above, in the case of V2X transmissionperformed by a V2X UE which moves relatively fast, more urgenttransmission is required often compared to the D2D transmission, andthus, the WAN transmission may not be always prioritized over the V2Xtransmission.

Accordingly, the following embodiment may be provided to solve theabove-described problem.

FIG. 23 is a flowchart of a V2X transmission method according to anotherembodiment of the present invention in the case where WAN transmissionand V2X transmission overlap in a time domain.

Referring to FIG. 23, when V2X transmission and WAN transmission overlapin a time domain and when the V2X transmission and the WAN transmissionare performed on different carriers, a UE may determine transmissionpower required for the VX transmission (S1410). The UE may be a V2X UE.More specifically, the following options may be provided.

Under the following options, by assigning a higher priority to a V2V TX(than WAN TX) when it comes to power allocation, it is possible toefficiently prevent degradation of V2V performance.

In this case, for example, when V2V TX occurs in a set time domain suchas “V2V gap” or when V2V TX with a (pre)set ProSe priority per packet(PPP) is performed, the following options may be applied limitedly. Inaddition, according to the following Option 2, solutions (or procedures)for dual connection may be reused.

Option 1: Power is first allocated to V2V TX and remaining power isallocated to WAN TX.

Option 2: Minimum power for V2V TX is guaranteed.

Herein, for example, (from the perspective of a specific (single) V2VUE), when V2X message TX and WAN UL TX (partially and/or entirely)overlap in a time domain on different (and/or same) carriers (orfrequencies), the following (some) rules are applied, and therefore,performance of V2V message TX (having a relatively high PPPP) and/or a(relatively important) WAN UL TX (e.g., PUCCH (or PRACH) (or PUSCH/SRS))may be guaranteed (as much as possible).

Herein, for example, the following (some) rules may be applied only inthe case where (time) synchronization difference between V2X message TXand WAN UL TX is greater than a pre-set (or signaled) threshold value.

(Example #1) “Guaranteed minimum power (G_MINPOWER)” may be set (orsignaled) on V2V message TX (equal to or greater than a pre-set (orsignaled) PPPP threshold value) and/or WAN UL TX (of a pre-set (orsignaled) channel (or signaled)).

Herein, for example, applying the pre-set (or signaled) G_MINPOWER valueto WAN UL TX (and/or V2X message TX) may be available only when a PPPPvalue of V2X message TX which overlaps (partially or entirely) (in atime domain) is greater than a pre-set (or signaled) threshold value(e.g., when the PPPP value of V2X message TX is smaller than the pre-set(or signaled) threshold value, power allocation to WAN UL TX isprioritized) (and/or when a sum of a (required) V2X message TX powervalue and a (required) WAN UL TX power value exceeds a UE's maximumtransmission power value (e.g., “23 DBM”).

Herein, for example, a G_MINPOWER value relating to WAN UL TX (and/orV2X message TX) may be set (or signaled) differently (or independently)for each PPPP value of V2X message TX (which overlaps (partially orentirely) (in a time domain)).

(Example #2) When a PPPP value of V2X message TX which overlaps(partially or entirely) (in a time domain) is greater than a pre-set (orsignaled) threshold value, WAN UL TX may be omitted (e.g., when the PPPPvalue of V2X message TX is smaller than the pre-set (or signaled)threshold value, V2X message TX is omitted).

Herein, for example, the corresponding rule may be applied limitedly inthe case of WAN UL TX except for a pre-set (or signaled) (important)channel (or signal) (e.g., PUCCH (or PRACH) (or PUSCH/SRS)).

Herein, for example, in the case of the pre-set (or signaled) importantchannel (or signal) (e.g., PUCCH (or PRACH) (or PUSCH/SRS)), theabove-described (Example #1) (e.g., G MINPOWER) may be (exceptionally)applied (e.g., which may be understood that transmission of the(corresponding) (important) channel (or signal) is not allowed to beomitted) and/or V2X message TX may be (exceptionally) omitted.

The above description may be summarized as below.

Proposal: To put it briefly, the following two options may supportprioritizing SL TX over WAN TX when it comes to power allocation.

(1) Option 1: First allocate power to V2V TX and remaining power to WANTX

(2) Option 2: Guarantee minimum power for V2V TX

(B) More detailed method for prioritizing V2X transmission (whichoverlaps with WAN (UL) transmission in a time domain on the same (and/ordifferent) carrier) over WAN (UL) transmission

FIG. 24 illustrates an example of a method for prioritizing V2Xtransmission (which overlaps with WAN (UL) transmission on a time domainon the same (and/or different) carrier) over a WAN (UL) transmission.

As illustrated in FIG. 24, a UE may perform V2X transmission and WANtransmission on the same carrier having a frequency of f0 at a time t0.FIG. 24 schematically illustrates the case of performing V2Xtransmission and WAN transmission on the same carrier for convenience ofexplanation, but the case of performing V2X transmission and WANtransmission on different carriers may be applicable in the followingembodiment of the present invention.

Herein, the following description may be applied for the above-describedcoexistence of PC5-based V2V and WAN.

First, sidelink open loop power control may bere used for V2V-relatedSL.

In addition, SL TX for V2V may be prioritized over WAN TX. In this case,the above-described SL TX for V2V may apply the above-described D2Doperation (e.g., Mode 1 and/or Mode 2). Herein, a priority may bemanaged by a base station (eNB).

In addition, the same receiver function of a D2C communication UE may beassumed even for a V2V UE. That is, if a UE is configured to receiveV2V, a RX chain may not affect WAN reception and may always receive aV2V signal.

Hereinafter, when WAN transmission and V2X transmission overlap in atime domain, a V2X transmission method will be described in more detail

FIG. 25 is a flowchart of a V2X transmission method according to anotherembodiment of the present invention in the case where a WAN transmissionoperation and a V2X transmission operation overlap in a time domain.

Referring to FIG. 25, when a V2X transmission operation and a WANtransmission operation overlap in a time domain and when the V2Xtransmission operation and the WAN transmission operation are performedon the same carrier, a UE may determine a priority of the V2Xtransmission (S1510). In this case, the UE may be the above-describedV2X UE. More specifically, options as below may be applicable.

For prioritization of SL TX through WAN TX, it is important to guaranteeV2V performance of TM 4 in a common carrier case (that is, SL TX and WANTX on the same carrier. As one possible option supporting thisoperation, reusing “ProSe gap” (e.g., a time period in which D2D TX setby a network is prioritized over WAN TX) together with additionalmodification optimized for a V2V traffic pattern may be considered.

In another example, always prioritizing V2V TX having a pre-defined PPPPover WAN TX may be considered. In other words, when V2V TX and WAN TXoverlap on the same carrier in terms of time, V2V TX having another PPPPmay be dropped.

Proposal: One of the following options may be selected to supportprioritization of SL TX over WAN TX.

Option 1: After application of several required modifications (e.g.,introduction of an additional period suitable for a V2V trafficpattern), “ProSe gap” related to Rel-13 eD2D may be reused. Herein, forexample, in the corresponding gap ((time (or frequency) resource)region, a V2V (message) TX associated with a PPPP (or a pre-set (orsignaled) specific PPPP) having a pre-set (or signaled) threshold valuemay be prioritized over WAN UL TX.

Option 2: V2V TX having a (pre) configured PPPP may be alwaysprioritized over WAN TX.

In conclusion, the above descriptions may be summarized as below.

Proposal: One of the following options may be selected to supportprioritization of SL TX over WAN TX.

(1) Option 1: After application of several required modifications (e.g.,introduction of an additional period suitable for a V2V trafficpattern), “ProSe gap” related to Rel-13 eD2D search may be reused.

(2) Option 2: V2V TX having a (pre) configured PPPP may be alwaysprioritized over WAN TX.

In another example, in the case of a P-UE(s), whether to (lastly)perform selection (or switching) between “(partial) sensing-basedresource selection behavior (or pool)” and “random resource selectionbehavior (or pool)” may be determined depending on whether “congestionlevel” (measured (directly) by the P-UE(s) or received from a differentV2X entity (e.g., a (serving) base station, and a V-UE(s))).

Herein, for example, if the “congestion level (which is measured(directly) by the P-UE(s), performing “(partial) sensing-based resourceselection behavior (or pool)”, or which is received from a different V2Xentity) exceeds the pre-set (or signaled) threshold value, “randomresource selection behavior (or pool)” may be performed (or used).

Examples of the above-described proposed methods may be included as oneof methods implemented by the present invention, and thus, it is obviousthat they can be considered as a kind of proposed methods. In addition,the above-described proposed methods may be implemented independently ormay be implemented in a combination (or integration) of some proposedmethods.

For example, in the present invention, a proposed method is describedbased on a 3GPP LTE system for convenience of explanation, but the rangeof systems to which the proposed method is applicable may include othersystems in addition to the 3GPP LTE system.

For example, the proposed methods of the present invention may beapplicable even to D2D communication. Herein, for example, the D2Dcommunication indicates communication in which a UE communicatesdirectly with a different UE, and, herein, for example, the UE is auser's terminal, but it may be considered a kind of UE when a networkdevice such as a base station transmits/receives a signal according to amethod for communication between UEs.

In addition, for example, the proposed methods of the present inventionmay be applicable limitedly only in Mode 2 V2V operation (and/or Mode 1V2X operation).

In addition, for example, the proposed methods of the present inventionmay be applicable not just to a P-UE(s) having a limited RX (or TX)circuit capability, but to a Vehicle UE(s) (V-UE(s)) (and/or a P-UE(s)having a non-limited RX (or TX) circuit capability).

In addition, for example, the proposed methods of the present inventionmay be applicable even when WAN UL TX and V2X message TX (partially)overlap in a time domain on different carriers.

In addition, for example, the proposed methods of the present inventionmay be applicable even when a P-UE (having a limited RX (or TX) circuitcapability) performs “partial sensing operation” (on (some) resourcesections (or regions) within a “sensing gap (or resource) received froma network (or base station) (or a RX gap (or resource) or a partialsensing gap (or resource))” and/or when the P-UE(s) (independently)performs “partial sensing operation” in a set (or designated) (some)resource section (or region) without receiving corresponding relevantinformation.

In addition, for example, the proposed methods of the present inventionmay be applicable limitedly only when a P-UE(s) (having a limited RX (orTX) circuit capability) performs “partial sensing” (and/or performs“full-sensing” operation (based transmission resource selection) (and/orrandomly select a transmission resource (without a sensing operation)).

In addition, for example, the proposed methods of the present inventionmay be applicable limitedly only when V2X message Tx and WAN UL TX(partially and/or entirely) overlap in a time domain on different(and/or same) carriers (or frequencies) (from the perspective of aspecific (single) V2X UE).

FIG. 26 is a block diagram of a UE that implements an embodiment of thepresent invention.

Referring to FIG. 26, a UE 1100 includes a processor 1110, a memory1120, and a Radio Frequency (RF) unit 1130.

According to one embodiment, the processor 1110 may implementfunctions/operations/methods described in the present invention. Forexample, the processor 1110 may receive pattern information used todetermine a sensing pattern, and sense some subframes determined fromamong subframes in a sensing window on the basis of the patterninformation, and select a specific subframe in the selection window as aV2X transmission subframe on the basis of the sensing.

The RF unit 1130 is connected with the processor 110, and transmits andreceives a radio signal.

The processor may include Application-Specific Integrated Circuits(ASICs), other chipsets, logic circuits, and/or data processors. Thememory may include Read-Only Memory (ROM), Random Access Memory (RAM),flash memory, memory cards, storage media and/or other storage devices.The RF unit may include a baseband circuit for processing a radiosignal. When the above-described embodiment is implemented in software,the above-described scheme may be implemented using a module (process orfunction) which performs the above function. The module may be stored inthe memory and executed by the processor. The memory may be disposed tothe processor internally or externally and connected to the processorusing a variety of well-known means.

What is claimed is:
 1. A method performed by a first user equipment (UE)capable of performing a first communication in a wireless communicationsystem, the method comprising: establishing a radio resource control(RRC) connection between an RRC layer of the first UE and an RRC layerof a base station; receiving first information related to a firstresource pool for the first communication; identifying at least onewindow for resource selection; performing sensing operation based on theat least one window in the first resource pool; receiving secondinformation related to resources for transmitting a vehicle toeverything (V2X) message; stopping the first communication on the firstresource pool based on the second information; generating an orthogonalfrequency division multiplexing (OFDM) signal including the V2X message;and transmitting the OFDM signal including V2X message on a secondresource pool based on the second information, wherein the secondinformation includes information related to a location of a second UEand informs that the second UE detects a second communication on thefirst resource pool, the second communication being different from thefirst communication and is undetectable by the first UE, wherein thesecond information is originated from the second UE, wherein the firstUE is incapable of detecting the implementation of the secondcommunication on the first resource pool while performing the firstcommunication, wherein the second communication is based on a radioaccess technology or a numerology that is different than the firstcommunication, and wherein at least one window comprises at least one ofa sensing window and a selection window.
 2. The method of claim 1,wherein the first UE incapable of detecting the implementation of thesecond communication is a UE having a limited sensing capability, a UEhaving no sensing capability, or a UE having no reception chaindedicated to the first resource pool.
 3. The method of claim 1, whereinthe first UE incapable of detecting the implementation of the secondcommunication is a Pedestrian User Equipment (P-UE).
 4. The method ofclaim 1, wherein the second information is received from the second UEor the base station.
 5. The method of claim 1, wherein the secondinformation comprises information indicating a type of a sidelinkservice which is performed on the first resource pool.
 6. The method ofclaim 1, wherein the second information comprises information indicatingwhether or not a service being performed on the first resource pool is apublic safety (PS) service.
 7. The method of claim 1, wherein the secondinformation comprises information indicating whether or notcommunication based on a radio access technology (RAT) different from aRAT of V2X communication is detected on the first resource pool.
 8. Themethod of claim 1, wherein transmitting the V2X message on the secondresource pool comprises: transmitting the V2X message on the secondresource pool for a preset period of time.
 9. The method of claim 1,wherein the second resource pool is a subframe other than a subframeused by the first UE in a previously transmitted Transport Block (TB).10. The method of claim 1, wherein the first resource pool comprises aV2X resource pool, a V2X carrier, a V2X channel, or a V2X band.
 11. Themethod of claim 1, wherein the second communication is detected bymultiple UEs including the second UE, and the multiple UEs are locatedin a pre-defined distance.
 12. The method of claim 1, wherein the firstUE is controlled to wake-up according to a pre-defined period to receivethe second information.
 13. The method of claim 1, wherein the secondinformation further informs whether the first communication is stoppedor is allowed on a different resource pool.
 14. The method of claim 1,further comprising: after receiving the second information, perform asensing operation on the second resource pool; and selecting a resourcefor transmitting the V2X message among resources where the sensingoperation is performed.
 15. The method of claim 14, wherein the resourcefor transmitting the V2X message on the second resource pool is selectedbased on at least one parameter related to a resource selection that issame as the first resource pool.
 16. The method of claim 1, furthercomprising: receiving a message informs whether a sensing operation isrequired to select a resource in the second resource pool or a randomselection of a resource is allowed in the second resource pool;selecting a resource for transmitting the V2X message among resourcesbased on the sensing operation, in case that the sensing operation isrequired; and selecting the resource for transmitting the V2X messageamong resources based on the random selection, in case that the randomselection is allowed.
 17. A first user equipment (UE) capable ofperforming a first communication in a wireless communication system, thefirst UE comprising: a transceiver; and a processor coupled to thetransceiver and configured to control the UE to perform operationscomprising: establishing a radio resource control (RRC) connectionbetween an RRC layer of the first UE and an RRC layer of a base station;receiving first information related to a first resource pool for thefirst communication; identifying at least one window for resourceselection; performing sensing operation based on the at least one windowin the first resource pool; receiving second information related toresources for transmitting a V2X message; stop the first communicationon the first resource pool based on the second information; generatingan orthogonal frequency division multiplexing (OFDM) signal includingthe V2X message; and transmitting the OFDM signal including the V2Xmessage on a second resource pool based on the second information,wherein the second information includes information related to alocation of a second UE and informs that the second UE detects a secondcommunication on the first resource pool, the second communication beingdifferent from the first communication and is undetectable by the firstUE, wherein the first UE is incapable of detecting the implementation ofthe second communication on the first resource pool while performing thefirst communication, and wherein the second communication is based on aradio access technology or a numerology that is different than the firstcommunication, and wherein at least one window comprises at least one ofa sensing window and a selection window.